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compulsory colour examination (in many cases a most inefficient one) to be passed before a sailor can become an officer, there is no check to a colour-blind man being a sailor, or to his remaining one to his life's end.
THE REV. T. A. Marshall describes in the November number of the Entomologist's Monthly Magazine a new genus and species of Belytidæ from New Zealand. The paper is accompanied by representations of two insects in fine condition. Mr. Marshall abstains from giving tedious details, as the figures will, he believes, convey a better idea of these creatures than many words, and he thinks they will now be unmistakable, at least until other species of the same genus shall be discovered. He has not taken any characters from the under-side, the specimens being carded; hence the oral organs could not be described, but they may be pretty safely assumed to resemble those of Belyta, Anectata, &c., and their details would have been of little value.
A CORRESPONDENT of the New York journal Electricity, writing from Paris, describes some electrical peculiarities which he has seen in a cat. This cat, called Michon, is a half wild animal, and dislikes handling. It belongs to the household of Dame Gais, whose residence on the Carnier Mount, near
Monte Carlo, looks directly down on the noted gambling casino and its botanical reservation. On some of the cold and very dry nights common to Monte Carlo in the winter, Michon, while in the dark, is quite a spectacle. Every movement of its body sends off hundreds of minute bluish sparks, something like those thrown off by ill-adjusted brushes, though not so pronounced in colour. They make a noise on a small scale, like the crackling of burning furze. Stroking the cat increases the sparking, and ruffling its fur the reverse way produces a miniature pyrotechnic display quite remarkable. The cat itself does not seem to mind the sparking, but, like all cats, dislikes to have its fur rubbed in a wrong direction. The writer has never seen
the electric element so abundant in a cat, and many who have seen the coruscations that have given notoriety Michon, confirm him in the opinion that the cat is an electrical curiosity.
A USEFUL account of "Biological Teaching in the Colleges of the United States," by Prof. John A. Campbell, of the University of Georgia, has been issued by the United States Bureau of Education. The writer's object is to present the actual extent and scope of the biological courses offered by the colleges of the United States, together with the methods of teaching employed. He also aims at presenting as fully as possible an account of the equipment and facilities for teaching which the various colleges possess. The statements he makes are therefore based largely upon the printed accounts found in the college catalogues, supplemented in many cases by letters containing additional information. These have usually been re-written, but where they are in suitable form they are quoted directly. Prof. Campbell notes that many of the colleges announce more in their catalogues than they can possibly do thoroughly with the teaching force employed. This is often perfectly apparent, but in more than one letter received the statement has been made that certain courses have no existence save on paper. Prof. Campbell, however, thinks that it is worth while to record the views of the professors in charge in regard to the nature and aims of such work, and the ideals towards which they are striving.
THE "Treatise on Hygiene and Public Health," edited by Dr. T. Stevenson and Mr. Shirley Murphy, and reviewed in NATURE last week, is published by Messrs. J. and A. Churchill,
MESSRS. J. AND A. CHURCHILL are publishing a second edition, revised and enlarged, of "Commercial Organic Analysis," by Alfred H. Allen. The second part of the third volume has just appeared. The third part of the same volume will be issued as soon as possible, and will complete the work. In the second part he has sought to describe fully and accurately such of the organic bases as have any practical interest, and to give trustworthy information as to their sources.
THE new number of Natural Science includes articles on the evolution of consciousness, by C. Lloyd Morgan; primæval man: a paleolithic floor near Dunstable, by W. G. Smith; the evolution of sharks' teeth, by A. S. Woodward; the walk of arthropods, by G. H. Carpenter; the falling of leaves, by A. B. Rendle; and Norwich Castle as a museum, by H. Woodward.
A REVISED edition of "London Birds and London Insects," by Mr. T. Digby Pigott, has been issued by Mr. H. Porter. Along with the essays on these subjects have been printed several other bright and attractive sketches.
AN elaborate index to the genera and species described in the "Palæontologia Indica," up to the year 1891, by W. Theobald, has just been issued. It is included among the Memoirs of the Mr. Theobald has also preGeological Survey of India. pared "Contents and Index of the Memoirs of the Geological Survey of India, 1859 to 1883."
A SECOND edition of Dr. F. H. Hatch's "Text-book of Petrology" has been issued by Messrs. Swan Sonnenschein and Co. The author explains that he has taken advantage of this opportunity to revise the book thoroughly, while largely increasing its scope.
THE Society for Promoting Christian Knowledge has published a second edition of Klein's "Star Atlas." Mr. E. McClure, the translator of Dr. Klein's explanatory text, has sought to bring up to date the German writer's descriptions of the more interesting fixed stars, star clusters, and nebulæ. MESSRS. ROBERT GRANT AND
SON, Edinburgh, and Messrs. Williams and Norgate, London, have issued Parts II. and III. of Vol. XXXVI. of the Transactions of the Royal Society of Edinburgh. The following are the subjects of some of the papers :-the foundations of the kinetic theory of gases (IV.), by Prof. Tait; the solid and liquid particles in clouds, by J. Aitken; the development of the carapace of the chelonia, by J. B. Haycraft; the composition of oceanic and littoral manganese nodules, by J. Y. Buchanan; the winds of Ben Nevis, by R. T. Omond and A. Rankin; and the Clyde sea area, by H. R. Mill.
its calendar for its twenty-first session, 1892–3. THE University College of Wales, Aberystwith, has issued
THE City and Guilds of London Institute has issued its programme of technological examinations for the session 1892-93.
MESSRS. GEORGE PHILIP AND SON announce that a work on "British New Guinea,” by Mr. J. P. Thomson, Hon. Sec. to the Brisbane Branch of the Royal Geographical Society of Australasia, is almost ready for publication. An appendix will contain contributions to the geology, fauna, flora, &c., by Sir William Macgregor, K.C.M. G., Baron Ferdinand von Mueller, Professor Liversidge, F.R.S., and others. The proof-sheets have been revised by Dr. H. Robert Mill and Dr. Bowdler Sharpe.
ANOTHER and apparently much more convenient mode of preparing glycol aldehyde, CH,OH.CHO, the first member of the series of aldehyde-alcohols, is described in the current number of the Berichte, by Drs. Marck wald and Ellinger, of
Berlin. It may be remembered that in our note of a fortnight ago (vol. 46, p. 596), it was announced that Prof. Emil Fischer and Dr. Landsteiner had succeeded for the first time in preparing this interesting substance in a state of tolerable purity by a reaction analogous to that of barium hydrate upon acrolein dibromide, the reaction which yielded the first synthetical glucose. They first prepared the mono-bromine, derivative of common aldehyde, CII,Br.CHO, and subsequently reacted upon this new substance, a liquid possessing an intolerably sharp odour, with baryta water. After removal of the baryta by sulphuric acid, and the hydrobromic and sulphuric acids by means of carbonate of lead, a liquid was obtained which possessed the properties of a dilute solution of glycol aldehyde. Some time ago Pinner obtained a derivative of this aldehyde which bore the same relation to glycol aldehyde, that the compound known as acetal, OC,HS CH.CH
bears to common aldehyde. This substance,
glycol acetal, CH2OH.CH
Pinner attempted to de
OC2H OC2HS' compose, by the action of mineral acids, into ethyl alcoholand glycol aldehyde. The attempt, however, did not succeed, inasmuch as the decomposition went further, any glycol aldehyde that may have been formed during the first stage of the reaction being subsequently broken up. Drs. Marckwald and Ellinger now find that the reaction succeeds admirably, provided the acid employed is extremely dilute, and as glycol acetal is a substance very easily prepared, they show that the reaction affords a very convenient and advantageous method of preparing large quantities of glycol aldehyde. The glycol acetal is added to an equal volume of water acidified with only a few drops of sulphuric acid. The liquid is then heated to boiling. After a short time the two liquids mix, and the reaction is completed when upon the addition of water to a few drops of it no separation of oil occurs. Upon distilling the liquid product, alcohol first passes over, then there distils a mixture of water and glycol aldehyde until decomposition of the residue commences. Glycol aldehyde, as thus obtained in a tolerably concentrated form, appears to be much more volatile in steam than was observed by Prof. Fischer and Dr. Landsteiner, in case of their more dilute solutions. From a few cubic centimetres of the distillate Drs. Marckwald and Ellinger obtained a very considerable quantity of Prof. Fischer's phenylhydrazine compound, and confirm in every detail the other properties of glycol aldehyde described in our previous note above referred to. The chemistry of this first member of the series which includes the sugars is now, therefore, fairly complete, and the difficulties in the way of its preparation surmounted.
THE additions to the Zoological Society's Gardens during the past week include a Rhesus Monkey (Macacus rhesus &) from India, presented by Mr. Pascoe Grenfell, F.Z. S.; Philantomba Antelope (Cephalophus maxwelli) from West Africa; three Gambian Pouched Rats (Cricetomys gambianus) from West Africa; a Ground Rat (Aulacodus swindernianus) from West Africa; and aWhite-faced Tree Duck (Dendrocygna viduata) from West Africa, presented by Mr. C. B. Mitford; a Martial Hawk-Eagle (Spizaetus bellicosus) from South Africa, presented by Mr. T. White; two Weaver Birds (Hyphantornis sp. inc.) from South Africa, presented by Mr. A. W. Arrowsmith; two Silver Pheasants (Euplocamus nycthemerus 8 8) from China, presented by Mr. E. Mitchener; a Common Chameleon (Chamæleon vulgaris) from North Africa, presented by Miss Kate Higgins; a Thick-tailed Opossum (Didelphys crassicaudata) from South America; a Garden's Night-Heron (Nycticorax gardeni); and two Saracura Rails (Aramides saracura) from South America, purchased; and a Squirrel Monkey (Chrysothrix sciurea) from Guiana, deposited.
Lying in the extreme northern corner of the constellation of Sextans, and nearly midway between p Leonis and Hydræ, it will not be an easy object for observation owing to its very late rising.
COMET BARNARD (OCTOBER 12).-Prof. R. Schorr, of Hamburg, communicates to Astronomische Nachrichten, No. 3125, the elements and ephemeris of Comet Barnard, deduced from observations made on October 16, 18, and 20, at Vienna, Hamburg, and Pulkowa respectively. As this ephemeris differs rather considerably from the one we gave last week, the following places may prove of service to observers :12h. Berlin M.T.
This comet will still be found to form approximately an equilateral triangle with a Aquila and 8 Delphini on November 5.
TABULAR HISTORY OF ASTRONOMY ΤΟ THE YEAR 1500 A.D.-Dr. Felix Müller, of Berlin, has just completed a small volume entitled "Zeittafeln zur Geschichte der Mathemathik, Phisik und Astronomie bis zum Jahre 1500," which will be welcomed by all interested in the very early history of the exact sciences. The book is arranged chronologically and gives a short account of the chief workers in these branches of science up to the year 1500. At the end of each reference a list of the literature likely to be needed is added. The work is published by Messrs. B. G. Teubner, Leipzig.
A LARGE TELESCOPE.-The Americans seem to have made up their minds to be the possessors of the largest telescopes in existence, for in spite of their owning the great Lick Refractor (36-inch) we hear now that the University of Chicago are about to have "the largest and most powerful telescope in the world.” This instrument will be the gift of Mr. Charles Jerkes, and will cost half a million dollars. The object-glass will have a diameter of 45 inches and will be made by Messrs. Alvan Clark, of Cambridge, Mass.
THE ATMOSPHERES OF PLANETS.-Of all the planets that revolve round our sun, Jupiter affords the most suitable of them for the study of atmospheric circulation. That his circulation will not be exactly like ours will be at once evident, for not only does the sun pour his rays on his vast surface, but he possesses himself heat, as is suggested by the rapid changes which these cloud masses undergo. A recent hypothesis, explaining the various movements in this planet's atmosphere, has been put forward by Mr. Marsden Manson, in the fifth number (vol. ix.) of the "Transactions of the Technical Society of the Pacific Coast," San Francisco. The chief element which produces these movements is the action of the sun, and it is on this reasoning that he attempts to unravel the laws underlying the circulation in Jupiter's atmosphere. In this pamphlet he first brings together some of the facts relating to our own wind system, which are generally conceded, together with the important results that were gathered from the path taken by the Krakatoa
In treating of the spots themselves, he suggests that those which are of a white appearance are gyrating uprushes of warm air from the lower regions, while the dark ones are simply descending columns of cool air, "the two forming parts of the system of vertical circulation." The red spot, he suggests, is caused by a local escape of internal heat, the repellent force it appears to possess being due to the "spreading of the heated currents as they rise." He explains the retardation and acceleration of its period of revolution by the increasing force of the west winds, brought about by the exposure of the southern hemisphere during Jupiter's half-year (5'93 of our years); in this way the spot is sometimes situated over and sometimes to one side of the source of heat
underneath. The author also deals with other spots in a similar
MR. SVEN HEDIN'S account of his ascent of Mount Demavend is published in the last number of the Verhandlungen of the Berlin Geographical Society. Demavend is a volcanic peak rising abruptly from the sedimentary rocks of the parallel Elburz chains. Starting from the village of Ranah on the southeastern slope with two guides on July 10, 1890, Hedin reached the summit on the afternoon of the next day. On the summit a large elliptical crater was found; the edges of which were strewn with blocks of porphyritic lava and sulphur. After discussing the aneroid and boiling point observations, Mr. Hedin arrived at 5465 metres (17,930 feet) as the height of the summit. This is lower than any of twelve earlier estimates which are cited, the highest of them being 6559 metres.
THE Italian possession of Eritrea on the coast of the Red Sea gives some promise of becoming useful agriculturally. Several small settlements of Italians on the plateau have succeeded in growing large crops of wheat and barley, and only the unsettled state of the surrounding natives threatens the prosperity of the farmers. The districts of Oculé-Cusai and Guro are already fully cultivated, and Saraé, as yet almost unoccupied, has fertile land and plenty of room for colonists. The Italians are able to work in climatic conditions which would rapidly exhaust the natives of northern Europe.
THE general summary of Mr. Conway's expedition in the Karakoram range telegraphed from India (p. 525) has now been supplemented by a full narrative, written to the secretaries of the Royal Geographical Society from a camp on the Baltoro Glacier on August 29, with a postscript added at Skardo, on the way to Leh, on September 12. The difficulties of the preliminary journey were very great, not the least being the fording of several swollen glacier streams by a party numbering four Europeans, four sepoys, seventy coolies, an indefinite number of followers, and flocks of goats and sheep. The moraines on the Baltoro glacier were of almost incredible extent; for two-thirds of its entire length the ice is entirely concealed by stones, except where crevasses or lakes occur, and the irregularity of the surface made travelling extremely slow. Mr. Conway limits the name of Godwin-Austen to the highest peak of "K2," giving to the whole mountain the somewhat cumbrous title of the Watch Tower of India. One branch of the Baltoro Glacier results from the union of seven glaciers from this mass; the larger branch descends from the snow-swathed, throne-shaped mountain, hitherto unmapped, for which the auriferous quartz found in its rocks suggested the name of The Golden Throne. This was fixed upon as the goal to be attained. The first attempt landed the Europeans and Ghoorkas, who made excellent climbers, on Crystal Peak, 20,000 feet in elevation, a peak as hard to climb as the Matterhorn, and isolated from the surrounding higher summits. No inconvenience was felt from the rarity of the air, and the party remained on the summit for an hour and a quarter. In the grand attempt on the Golden Throne serious difficulty was en
countered from the terrible extremes of heat and cold. last few thousand feet proved very exhausting; one of the Gboorkas had to be left behind, suffering from mountain-sickness. Every step had to be cut in hard ice. Finally the summit was reached at an elevation of 23,000 feet; but the Golden Throne stood revealed much higher, and separated by a deep depression. From the summit of Pioneer Peak, probably the highest yet reached by man, a series of photographic views was obtained and prismatic compass bearings taken to the surrounding features. As long as the party were at rest they felt no discomfort, but the sphygmograph showed that the heart's action was very laboured. A stay of an hour and a quarter was made on the summit, the view from which baffled description. The descent was safely made, but fatigue and bad weather stopped further exploration.
THE INSTITUTION OF MECHANICAL
ON the evenings of Wednesday and Thursday of last week, the 26th and 27th ult., an ordinary general meeting of the Institution of Mechanical Engineers was held in the theatre of the Institution of Civil Engineers, by permission of the council of the latter Society. The President, Dr. William Anderson, occupied the chair during the proceedings.
There were two papers on the agenda. The first was the report of the Institution's committee appointed to enquire into the value of the steam jacket. Mr. Henry Davey is the chairman of this committee, and he had prepared the report; which is a bare record of facts without comment, and in this respect is, we think, defective. Numberless experiments have been made in time past as to the value of the steam jacket, and those now added by the labours of the committee do not largely differ from many that have gone before. We take it that the general opinion of competent engineers is that an advantage in efficiency is to be obtained by jacketing engine cylinders in an efficient manner, and cases in which the jacket has not been proved efficient are those in which it has not been properly applied. What was wanted, therefore, was guidance as to the proper method of application, and it is significant that the most help in this direction came, during the discussion, from those who were not members of the committee. Timidity in expressing opinion will be excusably construed as indicating something of incompetence, and if the members are not capable of expressing opinion they are not suitable persons to form a research committee of an important institution. We frame our remarks hypothetically, because, with such names as Unwin, Bryan Donkin, and Mair-Rumley on the title-page, there can be no doubt that the power to afford guidance was present, and for this reason the decision to give only bare fact is the more to be regretted. The general conclusion to be drawn from the experiments, as quoted, is that "the expenditure of a quantity of steam in an efficient jacket produces a saving of a greater quantity in the cylinder.' It does not follow from this that the jacket is always desirable, as the saving may be so small as not to justify the additional complication and increased outlay at first cost. That, however, is a matter upon which steam users must themselves decide upon a commercial basis; and is, of course, outside the province of the committee, but what would have been valued would have been some critical remarks giving guidance as to what goes to constitute the "efficient jacket," what fresh engineering practice is opened up by the use of the efficient-jacket, and under what conditions it may be most effectually applied.
The first series of experiments quoted were carried out by Mr. J. G. Mair-Rumley, of the firm of James Simpson and Co., of Pimlico, upon a compound jet-condensing beam pumpingengine. The diameters of the cylinders are 29 inches and 47.5 inches, with strokes of 651 and 96 inches respectively. Only the body of each cylinder is jacketed, the steam being supplied direct from the boiler at a pressure of 49lbs. per square inch above atmosphere. Experiments were made both with and without steam in the jackets. The total feed water per indicated horse power per hour when the jackets were not in use was 18 20 lbs., with the jackets in use the corresponding figures were 16 64 lbs., thus showing a percentage of less steam used due to the jackets of 86. The quantity of jacket water condensed was 1 20 lbs. per I.H.P. per hour. The boiler pressure here was not high, 497 lbs. without and 49 lbs. with jackets.
The number of revolutions were also low, 14'8 without jackets and 15.78 with jackets. This was evidently an engine which should pay for jacketing. We next come to an experiment of a different nature, carried out by Mr. Davey and Mr. W. B. Bryan. The engine is triple expansion surface-condensing engine of the inverted direct-acting marine type, and is placed in the Waltham Abbey pumping station of the East London Water Works. The cylinders were 18", 30'5", and 51" in diameter, by 36 inches stroke. There is a Meyer expansion valve to the high pressure cylinder, by means of which the speed of the engine was regulated during the experiment. The bodies and both ends of all three cylinders are steam-jacketed. The jacket steam of the high pressure cylinder is at full boiler pressure, but the other two cylinders have the pressure reduced to a little above that of their steam-chests by means of reducing valves. Each cylinder is therefore jacketed with steam a little above its own initial pressure. Without the jackets in use the amount of feed water per I.H. P. per hour was 17 22 lbs, and with the jackets in use 15'45 lbs, showing a percentage of less steam used owing to the jacket of 10.3. The total jacket water was 172 lbs. per I. H. P. per hour. consumption is given in these experiments, being 2:09 lbs. per I. H. P. per hour without the jackets, and 1.79 lbs. with. The amount of coal burnt is not, of course, necessarily a measure of economy of the engine, but possibly the steam-generating plant -which included an economizer-was practically constant in its duty during both trials, and if so the commercial gain by the use of the jacket is quite an appreciable quantity. The boiler pressure here was 130 lbs. above atmosphere, the number of expansions without the jacket 22, and with the jacket 30. The revolutions were 23 per minute, so that the jacket had again a favourable chance.
The next series of experiments were carried out by Colonel English, Mr. Davey, and Mr. Bryan Donkin, and in these we reach a much higher piston speed, so that the results stand on a somewhat different footing in this respect to those before quoted. We have no positive knowledge of this engine beyond that given in the report, but it would be desirable to know something more of its working before accepting the very high percentage of gain in steam used-190 per cent.-as that due to a steam jacket used on a good engine. The feed used per I. H. P. per hour was 24.68 lbs. without the jacket, and with the jacket in use the quantity was 20 lbs. The following are the particulars of this trial:-Horizontal surface condensing compound engine, with intermediate receiver cylinders, 18 and 32 ins. by 48 ins. stroke. The ends of the cylinders are not jacketed, and the receiver jacket was not in use during the experiment. The boiler pressure was 50 lbs., the revolutions 57 06 without jackets, and 63 62 with, the feed water supply as stated, and the jacket | water condensed per I. H. P. per hour 1'13 lbs. The coal used without jackets was 3'26 lbs. per I.H.P. per hour, and with jackets 2'66 lbs.
The last set of experiments we shall quote were made by Prof. Unwin, upon the experimental engine at the City and Guilds of London Central Institution, South Kensington. It is a twocylinder horizontal-surface condensing engine, and can be worked either simple or compound. The cylinders are 8.73 inch and 15-76 in diameter, by 22" stroke. The high pressure cylinder is fitted with Hartnell expansion gear, and the low pressure with Meyer expansion gear. Only the bodies and the back ends of the cylinders are covered. We will first give results of trials working the engine with the low pressure cylinder only. The pressure was 60 lbs. above atmosphere, the jacket pressure being taken direct from the boiler. The revolutions without the jacket were 112'40, and with the jacket 101 73. The feed water per I.H.P. per hour without the jacket was 32'14 lbs., and with the jacket 26'69 lbs. This gives a saving of 17 per cent. working simple. It will be seen presently that when the engine was working compound, the saving was 7'3 per cent. The jacket-water per I.H.P. per hour was 1.88 lbs. We will now take the records of the compound trial. The boiler pressure was 6673 lbs. without the cylinders, and 67.80 lbs. with the jackets. The revolutions were 93.66 without the jacket, and 96:11 with. The feed water used per I.H.P. per hour was 21'06 lbs. without the jackets in use, and 19:52 ĺbs. with. The saving, as stated, made by the use of the jacket
1 This engine is stated in the report to have been fully illustrated and described in Engineering of November 16, 1888. The triple expansion engine at Waltham Abbey is also said to have been illustrated and described in the issue of August 8, 1895, of the same publication.
was therefore 7.3 per cent. The jacket water used per I.H. P. per hour was 2:40 lbs. We regret we are not able to give all the interesting details which Prof. Unwin includes in his instructive report, but for these we must refer our readers to the original paper.
Probably Prof. Unwin's 7.3 per cent. saving in steam used is a far better measure of the value of the jacket than the inflated promise of 19 per cent. in Major English's trial. It should be remembered that the jacket is more effective in small than in large engines, the area of cylinder will be in a higher ratio to the contained steam in the former than in the latter case. The number of expansions in the South Kensington engine working without jackets was 723, and with jackets 9:29. The corresponding figures in the case of the Woolwich engine were 9'4 and 126. The boiler pressure with the Woolwich engine was, however, 16 to 17 lbs. higher than in the other case. The revolutions were 57'06 and 63 62 respectively in the two trials at Woolwich, whilst at South Kensington they were 93 66 and 96 11. It would have been instructive if the committee had had the courage to attempt some balance of these figures, and then have endeavoured to account for the large difference which we believe would have remained still to be accounted for.
The next experiments quoted comprise a series made by Mr. Bryan Donkin, junr., at the works of his firm at Bermondsey. Mr. Donkin's labours in this field are well known, and engineering science is largely indebted to him for the contributions he has made to its lore. One most valuable feature in connection with these investigations is the means he has used to ascertain the temperature of the walls of the cylinder at various distances from the surface. In this lies the essence of the problem. If the Jackets Committee would give us minute and trustworthy information on this point we could evolve the rest from existing data. If we do not quote Donkin's figures in full it is partly because his experiments are not yet complete and partly because they have been dealt with more fully in "another place," namely, the Proceedings of a Society other than tha with which we are now dealing. We may state, however, that in one case when the steam in the jacket space was 298" Fahr. the cylinder walls averaged 290° Fahr., whilst at o 06 in. from the piston the temperature of the cylinder wall was 284° Fahr. These temperatures were ascertained by thermometers placed in holes drilled in the cylinder. Other instances are given, but the matter is far too interesting to deal with in a cursory manner, such as a report of this nature alone warrants. The difficulty that suggests itself is the fact that a thermometer itself has a very appreciable thickness, and the record will be but a mean of the temperature due to that thickness. It is possible that Mr. Donkin gets over this difficulty in some way. Perhaps the thermo-couple as used by Le Chatelier might afford a solution, although this (apparatus is not so useful for recording small differences at low temperatures, being rather adapted for such work as hot blast stoves and other metallurgical purposes. Mr. Bryan Donkin's experiments are the most suggestive in the report, as might be anticipated. Trials were made with steam at various rates of expansion to determine the effects of the steam jacket on the speed of engine and temperature of the cylinder walls, and on superheating, The engine used was a small one (6" x 8"), but it was specially constructed and arranged for the work. We again repeat Mr. Donkin's investigations are well worthy of the study of all interested in these matters.
The report concludes with a valuable appendix in the shape of suggestions for the use of those desirous of experimenting in this field.
The discussion on this paper was of a protracted nature, but was not of a kind altogether worthy of the leading mechanical institution of the country. Mr. Morrison, of Hartlepool, made the most weighty contribution amongst the speakers. He pointed out the difficulty of maintaining a good circulation of steam in the jacket-one of the most important points to which the designer of jacketed engines should turn his attention-and illustrated a simple method by which he had secured this end His arrangement consisted of a series of diaphragms, by means of which the steam was made to take a devious course through the jacket. Mr. Schonheyder pointed out a mistake the c mittee had made in placing an air-cock on the top of the jacket, when it was required to draw off air from the steam. Of course, this is one of those little slips which the wisest are apt to make, for it would be absurd to suppose such authorities as those ea1 See Proceedings Inst. Civil Engineers.
gaged did not know that air is heavier than steam. as well say one's grocer did not know sand from sugar. The Jackets Committee has not yet concluded its labours, and another report will be forthcoming in due course. Mr. Aspinall has offered a locomotive for trial, and we heard that Mr. Yarrow will put a torpedo boat at the disposal of the committee, and has even promised to cast special cylinders for experimental purposes. The locomotive will afford an interesting field of research, running as it does so largely linked up. The torpedo boat experiments will be no less interesting, especially in view of the great number of revolutions the engines of these craft make in a given time. On the second day of the meeting the paper by Mr. Walker of Bristol on the screw propeller. This paper gives the details of some experiments made by the author on a form of screw propeller invented by the late Mr. B. Dickinson. It would be in vain for us to attempt to condense this paper within the limits at our disposal. With regard to the merits of the Dickinson propeller we have nothing to say. It consists essentially of two narrow blades in place of one, and reminds us strongly of a Mangin propeller with one blade set somewhat back on the shaft. Mr. Walker contends that his researches prove the advantages of long narrow blades, but he did not appear to have converted the high authorities present, including Mr. Froude, Mr. Thorneycroft, and Mr. Barnaby-the three best-known names in connection with the subject-to his views. It is difficult to see wherein the value of the paper exists. Prof. Kennedy in the discussion stated that the generally received opinion as to the increase of the friction of the load was erroneous, and that the power absorbed in this way does not increase in the manner stated, a fact which he illustrated by means of a diagram. Mr. Thorneycroft pointed out that "life was not long enough" for the larger trials proposed by the author, but that he might decide one point if he would confine himself to models. Mr. Barnaby stated that a broad-bladed propeller should not be a uniform pitch. Mr. Froude's speech was a lucid criticism of the author's paper, the speaker pointing out in a kindly but convincing manner that the conclusions arrived at by the author might be subject to revision. Mr. Dunell, whose previous experiments the author had quoted, added to the information given by putting forward some other experiments he had made upon screw propellers fitted to a torpedo boat, in this case the results being opposed to those claimed by the author, inasmuch as the shorter and broader blade had proved the more advantageous. Mr. Shield, of Liverpool, described a form of propeller which has been in use on the Mersey, and appears to offer some advantages. The blades are attached to the boss in two parts, and are joined in a loop at the top. According to Mr. Shield's statement, the arrangement gives great advantages in towing, and also increased steadiness in running. The latter we can accept as a fact, but the great increase in towing capacity seems almost too good to be accepted literally. Twenty-five per cent. additional efficiency is a very large gain without further expenditure than an exchange of screws; but this is what the propeller in question
is said to realize.
The meeting concluded with the usual votes of thanks.
Matthey, so largely helped forward the principal work of the committee; the metallurgical studies of Stas are indeed recognized as veritable models of classical research in this particular field.
The new instruments added to the Bureau at Sèvres during the last year include a normal barometer (le Baromètre Fuess) and manometer, originally verified for reference as an international standard in accordance with the decisions of the Meteorological Conferences, particularly that at Munich last year. The committee have also obtained a new apparatus for determining the normal thermometric "boiling point," or the temperature of 100° Centigrade, as it has been found that the form of apparatus used by Regnault was unreliable for this purpose. In the reading of the standard manometer it would appear that higher accuracy has been obtained by raising the surface of the mercury up to a fixed point, the image of the point in the mercury being observed at the same time by means of a microscope. The Wild-Pernet barometer has been remounted, and the Bureau are now prepared to undertake the verification of any standard barometer.
The readings of all mercurial thermometers are given at the Bureau in terms of the hydrogen thermometer; and a 30litre holder for methyl chloride, or liquid carbonic acid, has been made by Brigonnet and Navile. The low temperature experiments have been continued by M. Chappuis down to -75° Cent.; and toluol and alcohol thermometers have been compared with the hydrogen thermometer. It has been found that "toluol" is more sensitive and reliable for low temperatures than alcohol.
We note that the meteorological work of the committee has largely developed itself; and that, as in geodetic research, the Bureau at Sèvres is now recognized as a central and international station of reference. Standard thermometers have been verified, for instance during 1892, for the Governments of Russia, France, and Roumania; for the Universities of Rome, St. Petersburg, and Odessa; for Owens College, Manchester; and for several recognized meteorological observatories. Great Britain has also been supplied by the committee with standard thermometers similar to those supplied to other contracting States.
Besides the standard metre and kilogramme already delivered to this country, the Bureau is undertaking the construction of a further standard metre for the Board of Trade, at a cost of 12,588 francs. The new standard appears to have been nearly two years in construction, but its verification is now promised
There are twenty-one different governments who have joined the Convention and who contribute annually towards the expenses of the Bureau (the annual budget of which is 75,000 francs), sums varying from 134 francs (Denmark) to 9482 francs (Germany) the annual contribution of Great Britain and Ireland for 1892 being stated at 4699 francs, or nearly £188; and that of the United States at 8471 francs.
undertaking an inquiry affecting measurement by light waves. By the use of the "Refractometer" Dr. Michelson found (Philosophical Magazine, April, 1891, and September, 1892) that accuracy of measurement by light waves may be increased to a high degree of accuracy. By the best spectroscopic instruments now in use it has been stated to be difficult to "resolve" lines as close together as the components of the yellow sodium
At the instance of Dr. B. A. Gould the committee are now also
INTERNATIONAL COMMITTEE OF WEIGHTS lines, but that if the width of the lines themselves be less than
THE International Committee of Weights and Measures, which was established in consequence of the Metric Convention of 1873, has recently issued its fifteenth annual report to the Governments represented at that Convention.1 The committee have also lately published the minutes of their proceedings (Proces-Verbaux des Séances. Paris, 1892. I vol. Svo) at the annual meeting held at Paris in September, 1891. It appears to be hardly possible that the proceedings of the committee at their meeting which was held last month may be issued before next year, but from the above publications, as well as from a recent volume of their "Travaux et Mémoires," we gather that they continue to carry on their investigations with all de-patch. In their last report the committee deplore the death of their colleague, Jean Servais Stas, whose analyses of the platinum alloys have, together with those of St. Claire Deville and George Rapport du Comité International. Gauthier-Villars. Paris. 1 Vol. 30 pp., 1893.
their distances apart, then there is no limit to their accuracy of with interest to the publication of Dr. Michelson's further results, measurement by the "Refractometer." We shall look forward
in the next volume of the "Travaux et Mémoires" of this committee.
Conservatoire des Arts et Metiers at Paris, for the adjustment The new instrument designed by M. Gustave Tresca, of the appears also to be better than anything yet adopted in England. and polishing of the terminal surfaces of end-measures of length
dards and instruments for the High Contracting Governments The committee not only undertakes the verification of stan(who have the right to demand such verification-), but they also readers, therefore, who may desire to have standards or instruverify for any scientific authorities or persons. To those of our be useful :— ments verified by the committee, the following information may
Applications for the verification of instruments should first be made to M. le Directeur du Bureau International (Dr. RenéBenoît), au Pavillon de Breteuil, Sèvres, près de Paris.