gation of the bromine addition products of angelic and tiglic acids, and was successful in showing that the two products were essentially different, exhibiting properties indeed so dissimilar that their identity was entirely out of the question. Although their similar constitution was indicated by melting-points differing by only one or two degrees, yet it was found that the crystals of the dibromide of angelic acid immediately reacted with water with production of a colourless oil, whilst the dibromide of tiglic acid remained unchanged in contact with water; moreover, the two compounds upon decomposition of their sodium salts, yielded two mono-brom-pseudo-butylenes, which differed essentially in their capability of reacting with alcoholic potash. In the year 1890, however, Prof. Fittig, of Strassburg, who had previously investigated the subject in conjunction with Herr Pagenstecher, and had obtained identical bromine addition products from the two acids, published a paper in the Annalen in which he sought to show that the results of Herr Pückert were incorrect, and that the two substances were identical. Prof. Fittig has since requested Prof. Wislicenus to withdraw the work or substantiate it, and further charges Prof. Wislicenus with seeing facts through the veil of his theory. Unfortunately Prof. Wi-licenus has been unable hitherto to meet the attack owing to domestic loss and serious illness, but at last he is able to publish the results of a really classical piece of work which he has carried through himself, and which not only demonstrates the truth of Herr Pückert's conclusions, but places the results beyond all criticism, and shows the singular cause of Prof. Fittig's inability to repeat them. It is indeed remarkable, but nevertheless true, that the fate of the theory of geometrical isomerism has actually been trembling in the balance owing to the different situation of the draught cupboards in the Leipzig and Strassburg laboratories. In the former laboratory they are placed between the windows, and in deep shadow; in the Strassburg laboratory they are against the windows, and are consequently brightly illuminated in daylight. Now Prof. Wislicenus shows that the dibromide of angelic acid is only formed in the absence of bright light, rays of daylight intensity being absolutely fatal to its formation. Hence Prof. Fittig only obtained the relatively more stable dibromide of tiglic acid, which in a good light is yielded by both angelic and tiglic acids. As the case is so remarkable, it may perhaps not be uninteresting to give a brief summary of the work of Prof. Wislicenus. One During the course of other researches concerning geometrical isomers, it was found that in order to obtain addition-products in which no internal re-arrangement of atoms had occurred, it was necessary to observe three conditions. must operate at the lowest possible temperature, exclude light as much as possible, and take care that the halogen to be added is always present in tolerably large excess. When these three conditions are observed, the two respective and distinct bromine addition-products of angelic and tiglic acids are always obtained. They are probably represented by the formula The operation of preparation is best conducted as follows: -A quantity of bromine, at least half as much again as is required by theory, and dissolved in three times its weight of carbon bisulphide, is placed in a flask surrounded by iced water. The flask is fitted with a triply bored caoutchouc stopper, through one hole of which is inserted a thermometer, through a second an exit tube furnished with a calcium chloride drying tube, and through the third the end of a burette containing a solution of pure angelic or tiglic acid in five times its weight of carbon bisulphide. The draught cupboard is darkened as much as possible and then the acid solution is slowly allowed to run into the flask. After the expiration of a few hours the formation of the brominated compound is complete, and the carbon bisulphide may be evaporated away in a rapid stream of dry air. The difference between the two compounds is apparent even at this early stage, for the tiglic compound commences to crystallize long before the removal of all the carbon bisulphide, and soon forms a snow-white mass of crystals. On the contrary, the angelic dibromide shows no sign of crystallization, remain ing as an oil for some time after the removal of all the carbor bisulphide. Eventually it crystallizes to a hard yellowish mas The only solvent from which it was found practicable to re crystallize the angelic dibromide was the pentane fraction petroleum ether boiling at 33-39°. The The melting-point of pure angelic dibromide is 865-87. of tiglic dibromide is 87.5-88. The two substances behave quit differently upon resolidification. The former congeals to transparent resinous mass, whilst the latter forms an opaqu solid. The most striking difference is apparent in their respectiv behaviour towards water. The dibromide of tiglic acid is on! slightly soluble in water, and dissolves unchanged, crystallizi out again upon evaporation. The dibromide of angelic acid, how ever, instantly combines with the equivalent of one molecule o water, to form a curious unstable liquid, an oil of high refractiv power, which is somewhat soluble in excess of water, and i again deposited upon evaporation. This liquid compound i also formed when the dibromide is exposed to moist air, while the dibromide of tiglic acid is not changed in a moist atmosphere In dry air the angelic liquid compound again dissociate into the dibromide and water vapour. In fact the dibromide angelic acid would appear to act as an excellent indicator of the hygroscopic state of the atmosphere. The two dibromides show a further difference in solubility the angelic compound being far more readily soluble in all th solvents experimented with. Free Finally the crystals of the two compounds, although bo belonging to the triclinic system, are absolutely unlike. measurements made by Dr. Fock, they are shown to exhib different forms, entirely different angles, and different dispositio of optic axes. From the above description it will be quite evident that th two compounds are certainly not identical. In conclusion, Prof. Wislicenus gives the results of attemp to obtain the dibromide of angelic acid in bright sunshine in t open air, then when working in front of a window, and aga when the experiment was performed upon a table in the centre the laboratory. In the first case, instead of the angelic com pound, 92.8 per cent. of the dibromide of tiglic acid was of tained, in the second case 896, and in the third case 88.7 p cent. These results render it perfectly clear why Prof. Fit could not obtain the angelic compound in his experiments, an they also show how it is possible for two chemists, both workin with a desire to ascertain the truth, occasionally to obtain resul apparently at complete variance with each other. A. E. TUTTON. MARINE LABORATORIES IN THE UNITE STATES.1 ONLY in comparatively recent times has the tremendo importance of the bearing of the invertebrates upon & general questions of biology been appreciated. We have see that some work was done upon these animals at an early da when the minds of workers were not much troubled by theore ical considerations, but the study of the adult forms is so sma a part of a real understanding of these animals that it w unsatisfactory work, and never became popular among invest gators until embryological methods had been introduced. 2 Dr. Brooks has remarked that "nearly every one of the grea generalizations of morphology is based upon the study of maris animals, and most of the problems which are now awaiting solution must be answered in the same way.' We find th reason for this in the fact that the biology of the present day a study of vital phenomena and of natural laws governing liv things. The importance of the invertebrates depends, there fore, upon the fact that in them life exists under simplified ditions, affording opportunities for the study of questions t which higher forms are, with our present knowledge, t complex. As the study of invertebrates has extended, it has becs more and more desirable to have more favourable conditions this work, more abundant facilities for collecting and opp Reprinted from Biological Teaching in the Colleges of the Un States," by John P. Campbell, Professor of Biology in the Universi Georgia; issued by the U.S. Bureau of Education. - Johns Hopkins University Circulars, vol. vi., p. 37. tunities for studying animals alive. Much of the early work was done upon specimens collected and stored in museums, but workers, both in this country and Europe, had frequently made excursions to the seacoast for the purpose of studying the invertebrate forms constituting so large a part of the marine fauna. The unsatisfactory nature of this work was of course evident. Suitable accommodations and working appliances could not be provided under these circumstances, and desirableness of establishing permanent seaside laboratories was early felt. Nothing was done, however, in this country until 1871, when John Anderson, a wealthy citizen of New York, presented to Prof. Agassiz the island of Penikese in Buzzard's Bay, together with the sum of $50,000 with which to found a seaside station for the study of marine life. Another friend gave him a yacht of 80 tons burden for use in collecting. Agassiz had =long wished for such a laboratory, and no one but himself could have aroused the necessary enthusiasm for carrying out the project. He soon set to work and built large aboratories, with suitable accommodations for a large number of workers. In 1873 they were opened for work. This constituted the first opportunity enjoyed by American students of studying marine animals in their native waters, with proper appliances for work. It inaugurated a new era in scientific research, being the first outward expression of an idea which has since taken a firm hold upon the investigators of the country. The death of Agassiz in December, 1873, put an end to the project. The buildings were used but two seasons and then abandoned. Of this laboratory Prof. Whitman says :— "At the close of the second and last season at Penikese, in 1874, Alexander Agassiz appealed to the colleges and all interested boards of education for support; but all in vain, for not a single favourable reply was received, and so his intention to remove the laboratory to Wood's Holl was never carried out. Thus that great and memorable undertaking, after absorbing money enough to build and equip a most magnificent laboratory, was abandoned from lack of interest on the part of educational institutions rather than of means. Such a failure, it must be frankly confessed, is not one to inspire confidence, but its explanation removes the apparent grounds for discouragement. It was the marvellous personality of Prof. Agassiz that made Penikese a possibility. It was his magic influence that created that school, his commanding individuality that organized and vitalized it. All interests centred in him so completely that with his sudden removal the enterprise was left without a soul. The school had no coherency except in his magnetic power and intellectual strength, and the moment these elements of stability were withdrawn, collapse followed as a natural and inevitable consequence. Then, too, it should be remembered that Prof. Agassiz lived just long enough to of the impracticability maintaining such demonstrate a school in such a locality, but unfortunately not long enough to convince the scientific world of its utility. The school was an experiment; its master was stricken down before it = could be fairly tested, and the times were not ripe for it." The establishment of this laboratory was an event of the greatest significance because of its bearings upon the history of education. Not only was Penikese the first biological station established in this country, and, indeed, in the world, but it was the beginning of the summer-school movement which has spread so generally over the country, and which, it should be noted, began with original research and finally extended to include the work of elementary instruction. The movement met with the cordial support of naturalists everywhere, and was almost immediately followed by the establishment of Dohrn's magnificent station at Naples. Soon after, in 1875, a seaside station was established at Helder by the Netherlands Zoological Society, and other smaller ventures followed in Europe. The need of opportunities for seaside study in the United States was too generally felt by those who had come under The Agassiz's influence for the project to be allowed to stop. advantages of this method of work over museum study had impressed themselves at least upon a few workers, and accordingly we find several attempts made to found new laboratories. They cliffered in character and aims, but all agreed in being founded upon the one idea of studying marine animals in their native waters. The most direct successor of the Penikese laboratory is the private laboratory of Prof. Alexander Agassiz at Newport. While this building is constructed on a much smaller scale than that at Penikese and is open only to a limited number of workers, yet it is prominent for the elegance of its appointments and its conveniences for work. The first laboratory for seaside study established in this country after the abandonment of Penikese was maintained by the Peabody Academy of Sciences, under the guidance of Prof. Packard, with the co-operation of Prof. Kingsley and others. This laboratory was for elementary instruction rather than research, and remained in existence only from 1876 to 1881. In 1878 the trustees of the Johns Hopkins University made an appropriation to allow a party of workers to spend some time in seaside study. The party was under the guidance of Dr. W. K. Brooks, who had himself been a pupil of Agassiz and a The location selected member of the Penikese laboratory. was at the lower part of the Chesapeake Bay, from which the name of Chesapeake Zoological Laboratory was chosen. No permanent buildings were erected, as it was intended, if possible, to change the location from year to year; but an outfit of boats and collecting apparatus was provided. The summers of 1878 and 1879 were spent about the lower part of Chesapeake Bay at Crisfield, Md., and Fort Wool, Va., at which places special attention was given to the development of the oyster. At the opening of the third season, in 1880, the need was felt of a locality that would offer a greater variety of objects for study, and accordingly the summers of 1880-82 were spent at Beaufort, N.C. This locality proved especially favourable, since sand bars, mud flats, salt marshes, and land-locked salt water, within easy reach, gave a large variety of different A rare forms, and there was also abundant ocean dredging. sufficient appropriation was made in 1880 to purchase a steam launch and a sloop, which put the workers in a position to take every advantage of their opportunities. In 1883 a special study of oyster beds made a return to the mouth of the Chesapeake Bay necessary, and that season was spent at Hampton, Va., but the following two seasons were again spent at Beaufort. In 1886 the need of a more southern location was felt, and The the Bahama Islands seemed to offer an inviting field. summer of 1886 was therefore spent at Green Turtle Cay, and the following summer at Nassau, New Providence. Financial difficulties temporarily stopped the work of the laboratory, but it is announced that it will be reopened in the summer of 1891.1 It is difficult to summarize the work of this laboratory, and It enjoys the none the less so to over-estimate its importance. distinction of being the first marine laboratory ever carried successfully into operation in the United States, and its work was entirely original research. The character of work done differed from year to year, according to the facilities which the different localities offered; but in general it may be said that embryology received most attention, while considerably less was devoted to The methods the discovery and description of new species. employed, as well as the new facilities enjoyed, made it possible to apply effective means of solution to many problems previously obscure, as well as opening many questions in regard to which nothing had been done. Of the lasting value of the work it is perhaps too early to speak, but the fact that over one hundred papers, based upon work there performed, have readily found publication in the best journals of this country and Europe, as well as the fact that much of the work has already found its way into standard textbooks, gives strong testimony to its value. The Chesapeake Zoological Laboratory may be regarded as the successor of the Penikese laboratory to the extent that its aims are the same, but it differed in not being generally open to the workers of the country. Arrangements were not made for large numbers, and those who were present were mainly students of the Johns Hopkins University. During the nine years that this laboratory remained in existence, there were in all fifty investigators present, and the average length of each session was nearly two months. The need was felt, especially in that portion of the country where Agassiz's influence was more directly exerted, of establishing a laboratory on a larger scale, and open to a larger 1 Shortly after the above was written, Kingston, Jamaica, was chosen as a suitable locality, and a party of advanced workers, numbering about fourteen in all, were present from May until September.-September 21, 1891. number of workers, and the first step taken in this direction was the founding of a laboratory by the Boston Society of Natural History. In their report for 1881 these words occur : "It has been considered desirable to found a summer laboratory sufficient to supply the needs of a class of persons who have begun to work practically under our direction, but have hitherto had no convenient means for pursuing their studies on the seashore. . We are sure that such a laboratory is needed for a limited number of persons, such as our own pupils in natural history, and some of the teachers of the Boston public schools, about a dozen in all, but we are not sure of any real demand outside of these." Arrangements for laboratory work were speedily made at Annisquam, Mass. Boats and appliances for collecting were at once provided, and in the spring of 1881 a circular was issued announcing the opening of the new laboratory. From this the following extracts are taken : "The liberality and co-operation of the Woman's Educational Association enable the Boston Society of Natural History to announce that a seaside laboratory, under the direction of the curator (Prof. Alpheus Hyatt), and capable of accommodating a limited number of students, will be open at Annisquam, Mass., from June 5 to September 15. "The purpose of this laboratory is to afford opportunities for the study and observation of the development, anatomy, and habits of common types of marine animals, under suitable direction and advice. There will, therefore, be no attempt during the coming summer to give any stated course of instruction or lectures. "It is believed that such a laboratory will meet the wants of a number of students, teachers, and others who have already made a beginning in the study of natural history." Twenty two persons were attracted to the Annisquam laborat ry during its first season. Prof. Hyatt, in his report for 1882, remarks as follows: "The great need of an institution for teaching field work cannot be properly estimated by the number of those who are attracted by the opening of such opportunities for study. The mental condition of those who attend, and what it has done for them, and the sphere of influence which it reaches through them, are the only true standards by which its present and future usefulness can be properly measured. Nearly all the pupils were persons who could be termed 'well educated;' nevertheless they were, with the exception of some who had already worked in the laboratory or field, entirely unable to obtain knowledge with their own eyes and hands, and had even acquired a notion that this was not possible for anybody except the trained man of science. Several of these teachers, after their work was finished, expressed their gratefulness for the new powers the course had developed in themselves, and the fascinating pleasure they had experienced in learning to use their own eyes and hands in the study of things hitherto unapproachable for their uncultivated senses except through the deceptive mediation of books. When it is remembered that these teachers influence and mould the minds of thousands of young persons it is at the same time proved that what this laboratory has done and can do is not to be estimated by the number of its own pupils." The success of the undertaking seemed assured, and arrangements were made for its continuance during the five years following. The number of students fluctuated greatly, falling to ten in the third year, and running up in the sixth year to twenty six. During these six years the laboratory was carried on jointly by the Boston Society of Natural History and the Woman's Educational Association of Boston. It has been the policy of both of these associations to originate new enterprises, but to turn them over when well started into other hands. It seemed in 1887 that the time had come when the maintenance of the laboratory should be put on a firmer basis. It had been supported long enough to demonstrate its practicability and usefulness. The demands upon it had increased. It was no longer an experiment. The associations believed that a permanent organization should be effected, the working facilities increased, and the whole established on a larger scale. Moreover, it seemed that something more might be done to give the laboratory a wider sphere of usefulness in advancing knowledge of marine like. Great as was its work in teaching, it seemed to depend for its support upon a circle of people too small for the extent of its benefits. It seemed desirable that a change should come which would lead to a more widespread interest in the laboratory, and bring together more investigators. T Marine Biological Laboratory was the result of this movemen While space will permit but a brief account of this h ratory, its history, development, aims, &c., it may be that the one point which distinguished it from the Annisq laboratory was the prominence given to research. Students received, but from the outset there has been a settled des mination to so adjust the claims of each as to secure the gree amount of efficiency and do most to advance science. Th organization was therefore effected so as to secure a perman staff of investigators, who would always be present, increas knowledge by their own work, and by their example stimulata others to follow. Moreover, the principle was thoro recognized that the best investigation is prompted by the w of teaching. The best investigator is often the best teacher but the work of teaching reacts upon the work of investigation influencing it for the better. The experience of the laboratory shows that these poin which had previously been carefully considered, were well take Various means were resorted to for providing funds, and a March, 1888, the laboratory was incorporated. Wood's Holl was chosen as a locality because of its co venience, accessibility, and the variety of its land and mar flora and fauna. The building was at once begun, and finishe in time for work during the summer. Circulars could not issued until after most of the colleges had disbanded for th summer, and yet during the first season seven investigators and eight students were attracted to the laboratory. when In subsequent years the growth has been a steady one. The number of workers has greatly increased, and even now, only its third season has been passed, it is stated that the spat is insufficient to meet the demands upon it; the facilities for collecting are too small, and the staff of instructors is not large enough for their classes. Its usefulness is now established, and the time is ripe for it. To it in great measure the United States must look for the advancement of biology. Let us hope that its trustees, all of whom are working biologists, may be successful in placing the laboratory upon such a financial bass that its full possibilities for usefulness may be realized. UNIVERSITY AND EDUCATIONAL CAMBRIDGE.-Dr. Hill, Master of Downing College, ha been appointed Chairman of the Natural Science Tripos Examiners for 1893. An election to an Isaac Newton Studen ship in Astronomy, Astronomical Physics, and Physical Optics, will be held in the Lent term 1893. Candidates must be B. A.'& and under twenty-five years of age on January 1. The emot ments are £200 per annum for three years. Applications are to be addressed to the Vice-Chancellor between January 17 and 27, with testimonials or other evidence of competency. The Dr. Lorrain-Smith, M.D. Edin., Demonstrator of Physiolog at Oxford, and Dr. F F. Wesbrook, M D., Manitoba, Pre fessor of Pathology at Winnipeg, have been elected John Luck Walker Students in Pathology. The Managers express the high approval of the valuable researches conducted by the late student, Dr. A. A. Kanthack, of St. John's College. State Medicine Syndicate state that, at the two examinations held in April and October, 1892, there were in all sixty-four candidates, of whom thirty-five received Diplomas in Pul.: Health. The fee in future will be five guineas for each of the two parts of the examination in State Medicine. Examinations for open scholarships and exhibitions Natural Science will be held in twelve of the Colleges December and January next. A list giving the conditions an value of the scholarships is published in the University Repor of November 12, pp. 198, 199. SCIENTIFIC SERIALS. Wiedemann's Annalen der Physik und Chemie, No. 10Refraction and dispersion of light in metal prisms, by D. Shei Thin prisms of gold, silver, nickel, and cobalt were prepared the electrolysis of cyanide solutions by Kundu's metho Prisms of platinum were also prepared by the disintegration platinum foil. A piece of foil 4 mm. broad and 0.02 thick placed perpendicularly to a piece of plate glass at a de tance of 0.5 mm. produced under the action of a current of 2 amperes a double wedge-shaped layer of oxide in half an hour his was easily reduced by a Bunsen flame, so as to represent metallic prism with an angle of some 20 seconds. Only one twenty of the prisms could be used, and only one in 200 silver gold prisms. The source of light was a zirconium burner ith a red shade transmitting light of the mean wave-length x 10 cm. The index of refraction was found to vary with incidence. For perpendicular incidence the following alues were found: Au o'26, Ag o'35, Cu 0'48, Pt 1'99, Ni 01, Iron 302, Co 316. For silver the index was 0.39 at an cidence of 10°, 0·60 at 30°, 0.80 at 50°, 1'01 at 80°, and I'03 90°. The following refractive indices for various waveengths illustrate the dispersion : Li, a 0'29 0 25 0'35 2'02 D 0.66 0'27 0'60 1'76 F 0.82 O'20 I'12 1.63 ... G 0'93 0'27 1'13 1'41 On a law of refraction for the entrance of light into absorptive pedia, by H. E. J. G. du Bois and H. Rubens.-On the infraed emission spectra of the alkalies, by Benjamin W. Snow. Absolute change of phase in light by reflection, by Paul Glan. -Inducti e representation of the theory of double refraction, by Franz Kolácek.-Studies in the electric theory of light, by D. A. Goldhammer.-On the passage of feeble currents through lectrolyte cells, by Rud. Lohnstein.-On the motion of the ines of force in the electro-magnetic field, by Willy Wien.-On he electric theory of magneto-optic phenomena, by D. A. Goldhammer.-An automatic interruptor for accumulators, by 1. Ebert. This is to prevent the current from the accumulator :xceeding the supply for which it is constructed. Two mercury ups are inserted in the circuit, connected by a piece of stout cop>er wire. The current next passes through an electro-magnet. As oon as the current reaches a certain strength the electro magnet ›verpowers an adjustable spring, and lifts the copper connecting. piece out of the cups.-Contribution to the history of the pheroidal phenomena, by G. Berthold. SOCIETIES AND ACADEMIES. LONDON. Physical Society, October 28.-Dr. J. H. Gladstone, F.R.S., past president, in the chair. -The discussion on Mr. Williams's paper, "On the relation of the Dimensions of Physical Quantities to Directions in Space," was opened by Prof. Perry eading a communication from Prof. Fitzgerald, president. The writer said Mr. Williams disagreed with the suggestion that lectric and magnetic inductive capacity are quantities of the ane kind principally because he had not got over the curious rejudice that potential and kinetic energy are different. No heory of the ether could be complete unless it reduced its energy the kinetic form. Electric and magnetic inductive capacity ould probably be found to be similar in the ether, and ultiately have the same dimensions, The analogies were not yet mplete, but only in respect of matter was it probable that any fference existed between them. Diamagnetism corresponded to ectrostatic induction, but paramagnetism had no definite ectrical analogue. He was inclined to regard the phenomena paramagnetism as connected with the arrangement of the terial molecules, whilst diamagnetism depended on the ctric charges on those molecules. So far no matter had been and which conducts magnetism, and such may not exist in our verse, but it may be gravitationally repelled by matter as we ow it.-Mr. Madan remarked that in the first part of his er Mr. Williams recognized that dimensional formulæ were ginally change-ratios, but puts this aside for the higher conon which regards the e formulæ as expressing the nature of quantity. Fourier showed how to find the dimensions of ts by making the size of the fundamental units vary. But pecific inductive capacity) did not vary with the fundamental ts, for it was merely the ratio of the capacities of two consers, and therefore, by Mr. Williams's definition, a pure ber. It was difficult, he said, to see how k could have ensions, but Mr. Williams regarded it as a physical quantity, therefore possessing dimensions. The object in giving ensions to k and seemed to be to get over the double em of units. Mr. Madan did not think that dimensions d express the nature of physical quantities, and said differs of opinion existed amongst authorities on this point. For aple, Dr. J. Hopkinson, at the last B. A. meeting, said that use a co-efficient of self-induction had the dimensions of length it must be a length, whilst other learned professors objected to this view. Even if one admitted that dimensions are a test of the nature of physical quantities it was not necessary that the two systems of units should be identical. The connecting link between the two systems was QC t, and the validity of this equation had been questioned. If this objection be confirmed, then there would be no current in electrostatics and no Qin the electromagnetic system, and the units would not clash. Referring to dynamical units, Mr. Madan pointed out that two units of mass were used in astronomy, but astronomers got over the difficulty by using a co-efficient. Dimensional formulæ, he said, are the result of a convention that certain definitions should hold true generally, but they contain no further information respecting the nature of the quantities beyond that involved in those definitions. As an example of the inability of such formulæ to express the nature of quantities, he pointed out that whilst physical differences were known to exist between + and - electricity the dimensional formulæ showed so signs of such differences.-Prof. Rücker said every correct physical equation consisted of a numerical relation between physical quantities of the same kind, and might be written either as a mere numerical equation or as a relation between the physical quantities themselves. The equation 2+ I = = 3 correspond to 2 feet + I foot = 3 feet, and latter may be written 2[L] + 1[L] = 3[L], where [L] represents the unit of length. So far as he was aware, nobody but a recent writer in the Electrician had denied that in such an equation [L] represented a concrete quantity. Maxwell explicitly stated that it does in his article on "Dimensions" ("Encyl. Britt.") and elsewhere, and Prof. J. Thomson, in his paper on the same subject, makes no statement contrary to this. The above equation might also be written 2[feet] + [foot] I[yard]. Another equation involving time is 60[sec.] I[minute], and dividing one by the other one gets = foot sec. Prof. Henrici said the communication under discussion was one of the Lost important contributions to physical science which he had come across for a long time. Such difficulties as presented themselves in the paper arose from its fundamental character. The author had attempted to express all physical quantities in terms of three, but quantities may exist which cannot be completely represented in terms of L, M and T. The tendency of modern mathematics was to express everything dynamically. Mathematicians had long been in the habit of using quantities which were neither numbers nor concretes in the ordinary sense, and different kinds of algebra with units not understandable had been developed. If a quantity, a times a unit u, be multiplied by 6 times another unit v, the result is expressed by ab uv, where ab is a number and uv a new unit which may or may not be physically interpretable. The interpretation of a product depended on the meaning attached to multiplication," and if this be restricted to "repeated addition the range is very limited. The narrow conceptions concerning multiplication acquired at school could only be removed by a careful study of vectors. Mr. Williams had treated his subject by vector methods, but a few traces of quaternions remained which might be omitted. To truly understand the subject, vectors must be treated vectorially. Dimensions might then show the nature of the quantities involved. The system adopted in Mr. Williams's paper was probably the best attainable at present, but he (Prof. Henrici) looked forward to the use of a more fundamental quantity than the vector-viz. "the point "- -as the ultimate basis. Grassmann had worked out a "point calculus" in 1844, which was republished in 1880. Quantities more complex than vectors, viz. rotors, screws, motors, &c., had been used with advantage by Clifford, Ball, and others. Dr. Sumpner thought the first ideas of students on the subject of dimensions were that they represented the nature of the quantities, but could not see why every quantity should be expressed in terms of L, M and T. Prof. Rücker's paper on "Suppressed Dimensions" had cleared up several important points, and he (Dr. Sumpner) now considered that every quantity must be expressed in terms of a unit of the same kind as itself. He viewed Mr. Williams's attempt to express everything in terms of L, M and T, as rather a retrograde step. The discussion on Mr. Williams's paper was adjourned, and Dr. Young made some remarks on Mr. Sutherland's communication "On the Laws of Molecular Force." Mr. Sutherland, he said, thought that Ramsay and Young's law ap/ƏT = ƒ (v) is not correct for compounds in the liquid state. Barus, however, had proved that several liquids, including ether, only showed variations from the law at extremely high pressures. After writing the equation of the virial in the form po = RTvf(v) +vq(v), where vp(v) stands for the internal virial term; the author of the paper had shown that (v) ought to be constant, but, finding it not constant in the case of ether, &c., he attempted to explain the discrepancies by the formation of pairs of molecules at small volumes. Other substances, such as nitrogen and methane, were supposed to follow the law. This, Dr. Young said, could not be accepted as proved, for the range of volumes over which the experiments had been made was only small, and methane was difficult to prepare pure. After criticizing the use of two and sometimes three "characteristic equations" for the same substance, he went on to show that the formulæ given in the paper by which the critical temperatures, pressures and volumes might be calculated, lead to results differing from experimental numbers by quantities greatly in excess of experimental errors. Experiment also showed that capillarity had little or no effect on the determination of critical constants. Speaking of critical volumes he pointed out that MM. Cailletet and Mathias had published a method of finding critical densities which gave very accurate results. Mr. Sutherland's conclusions respecting Van der Waals's generalizations were practically identical with those expressed by Dr. Young in his paper on the subject, read before the Society last year. The views as to the nature of the various kinds of "pairing mentioned in Mr. Sutherland's paper were open to serious objections, for his "physical pairing" is supposed to produce more effect on the "characteristic equation than true chemical pairing. In his (Dr. Young's) opinion the idea of physical pairing appears somewhat speculative and requires further elucidation.-A paper on the determination of the critical density, by Dr. Young and Mr. A. L. Thomas, and two papers, on the determination of the critical volume, and on the boiling points of different liquids at equal pressures, by Dr. Young, were taken as read. The first paper gives an account of results obtained by Cailletet and Mathias's method, based on the fact that the means of the densities of a substance in the states of liquid and saturated vapour when plotted with temperature, lie on a straight line which passes through the critical point. In the paper on critical volumes the above-mentioned method is again referred to and results obtained thereby accepted in preference to those given by the author in his paper on Generalizations of Van der Waals, &c., read before the Society about a year ago. The alcohols do not strictly follow the straight-line law. Revised tables of critical volumes, densities, pressures, and temperatures are given, and it is pointed out that for many substances the ratio of the actual critical density to the theoretical density (for a perfect gas) is about 3.8. The paper on boiling-points of different liquids at equal pressures contains a comparison of the accuracies with which a formula for the relation between the boiling-points given by M. Colst (Compt. Rend., cxiv. p. 653), and one by Ramsay and Young (Phil. Mag., January 1886), accord with experimental results. The author concludes that the latter formula shows the best agreement, but that of M. Colst is satisfactory under certain conditions. The further discussions of Mr. Williams's and Mr. Sutherland's papers were adjourned till the next meeting. Mineralogical Society, October 25. At the Anniversary Meeting the following were elected Officers and Members of Council-President, Prof. N. S. Maskelyne, F.R.S.; VicePresidents, Rev. Prof. S. Haughton and Dr. Hugo Müller, F.R.S.; Treasurer, Mr. F. W. Rudler, F.G.S.; General Secretary, L. Fletcher, F. R. S.; Foreign Secretary, Mr. T. Davies; Ordinary Members of Council, Prof. A. H. Church, F.R.S., Prof. Grenville A. J. Cole, Mr. T. W. Danby, Dr. C. Le Neve Foster, F.R.S., the Rev. H. P. Gurney, Mr. J. Horne, Prof. J. W. Judd, F.R.S., Prof. G. D. Liveing, F.R.S., Lieut. General C. A. McMahon, Mr. H. A. Miers, Mr. F. Rutley, and Mr. J. J. H. Teall, F.R.S.-Dr. C. O. Trechmann detailed the results of the goniometrical measure ment of two very perfect crystals of Binnite collected himself in the Binnenthal. The measurements, besides ad a large number of forms to those previously recorded for species, serve to establish the tetrahedral hemisymmetry of mineral which has been left as a very doubtful feature by vious observers, and was denied by Hessenberg-Mr. H Miers and Mr. G. T. Prior announced the results of fer researches on the rare silver minerals known as Xanthoc and Rittingerite. According to their physical measureme and chemical analyses these two substances are identical, bri having the same composition as Proustite, and crystallizing rhombic-shaped tables belonging to the mono-symmetric sys The name Xanthoconite, given by Breithaupt, has the prior the red-silver ores are now to be regarded as an isodimorphous group consisting of the two sulph-arsenites Proustite and X thoconite, and the two sulph-antimonites Pyrargyrite and F blende. Previous determinations of the composition of Kit gerite and the crystalline form of Xanthoconite have be erroneous.-Mr. Fletcher gave a description of a new hab Descloizite from the Argentine, and also an account of the as mineral Baddeleyite (native zirconia): the only fragment as y found is part of a twinned crystal showing forms which belong the mono-symmetric system: pleochroic: optically negat and biaxal with inclined dispersion: specific gravity 6 hardness 6.5.-Mr. Allan Dick contributed further remarks Geikielite, supplementing his paper read at the previous me ing.-Prof. Judd exhibited photographs in illustration of previous paper on the lamellar structure of quartz crystals an the method by which it is developed. —Mr. Rutley exhibet large series of beautiful cardboard models illustrative of symmetry and optical characters of the crystalline systemsMr. Miers exhibited specimens, including the rare mineral nerite from the Tintagel Slate quarries which he had visited search of that mineral. Zoological Society, November 1.-Sir W. H. Flowe F.R. S., President, in the chair.-The Secretary read a re on the additions that had been made to the Society's Menager during the months of June, July, August, and September, 18 and called special attention to a young Gibbon from Hai South China, of a uniform black color, belonging to the species recently described by Mr. Oldfield Thomas as Hy hainanus, presented by Mr. Julius Neumann, and to a ye male Malayan Tapir (Tapirus indicus) from Tavoy, Burc (on behalf of the Hon. Walter Rothschild) exam presented by Col. F. M. Jenkins.-Mr. E. Hartert exhib of two new Mammals from New Guinea (Proechidna nig aculeata and Acrobates pulchellus), and a stuffed specimen Apteryx maxima from Stewart Island.-A communication read from Lord Lilford, giving an account of the breeding pair of Demidoff's Galagos in his possession.-Prof. Bell re a note on the occurrence of Bipalium kewense in IrelandMr. Finn gave an account of his recent zoological excursion Zanzibar.-Prof. Newton, F. R. S., exhibited and made remar on a specimen of Sylvia nisoria lately killed in England.-Fr F. Jeffrey Bell read a description of a remarkable new spec of Echinoderm of the genus Cidaris from Mauritius, prop to be called C. curvatispinis.-A communication was from Sir Edward Newton, and Dr. Gadow, F.R.S., describe a collection of bones of the Dodo, and other extinct bir Mauritius, which, having been recovered from the Mare Songes in that island by the exertions of Mr. Theodore Say had been by him entrusted to them for determination. collection contained examples of the atlas, metacarpals, pelvic vertebra, and complete pubic bones of the Dodo, w had before been wanting, as well as additional remain Lophopsittacus, Aphanapteryx, and other forms already kn to have inhabited Mauritius. Besides these there were bot of other birds, the existence of which had not been suspec and among them of the following, now described as new Strix (?) sauzieri, Astur alphonsi, Butorides maur: Plotus nanus, Sarcidiornis mauritianus and Anas theod whole adding materially to the knowledge of the original of Mauritius. Mr. Oldfield Thomas gave an account of lection of Mammals from Nyassa-land, transmitted by Mr H. Johnston, under whose directions they had been ob by Mr. Alexander Whyte.-Dr. Günther, F.R.S., read a descriptive of a collection of reptiles and Batrachians Nyassa land, likewise transmitted by Mr. Johnston, and taining examples of several remarkable new species, am which were three new Chameleons, proposed to be |