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admitted that this conclusion needs confirmation from future discoveries before it can be definitely accepted. The specimens on which the new genera Coryphænopsis and Bayeria (Fritsch) are founded are certainly remarkable.

Dr. Fritsch's section of the work shows that all the usual groups of Cretaceous Reptilia are represented in the Bohemian rocks. There are undoubted fragments of Plesiosaurs, and there is one interesting brain-cast which the author describes as probably referable to Polyptychodon. Dr. Fritsch, however, overlooks the fact that the skull of Polyptychodon is actually known in England, and is undoubtedly Plesiosaurian or Pliosaurian, not Mosasaurian. Chelonian remains occur, evidently representing turtles related to the small Chelone Benstedi from the English Chalk. Some fragments appear to be Mosasaurian, but those described under the new name of Iserosaurus litoralis are extremely problematical. Other fragments, ascribed without much reason Dinosauria, scarcely suffice to justify the new names bestowed on them. Some good new figures of the interesting wing-bones of the small Pterodactyl, Ornithocheirus hlavaci, are given, and the volume concludes with a systematic list of species.

A. S. W.

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Die Bedeutung des Experimentes für den Unterricht in der Chemie. By Dr. Max Wehner. Pp. 62. (Leipzig and Berlin: B. G. Teubner, 1905.) Price 1.40 marks.

THIS brochure forms part of a "Sammlung naturwissenschaftlich-pädogogischer Abhandlungen," and is very hard reading for an ordinary English chemist. It is divided into two parts, the first of which deals with the importance of experiment for attaining the object of chemical instruction, and the second with the importance of experiment in relation to method in chemical instruction. It is hard reading in the sense that one has to wade through detailed arguments which culminate in conclusions such as "description does not suffice for the instruction of the pupil in chemical processes," and "the development of the laws concerning chemical processes from experimental observations is more effective for chemical teaching than their deduction from quoted examples." The work is, in fact, an example of pure pedagogical exercitation, and it may be recommended with confidence only to those who have a liking for that kind of literature. A. S. Monographie des Cynipides d'Europe et d'Algérie. By l'Abbé J. J. Kieffer. Tome second. 2me. fascicule. Pp. 289-748; plates ix-xxi. (Paris: A. Hermann.) Price 18s.

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THIS is the conclusion of vol. vii. bis of André's great series of monographs, Spécies des Hymenoptères," and completes the Cynipides, or gall flies. The previous portions have already been noticed in NATURE (vol. lxvii. pp. 124-5, December 11, 1902, and vol Ixviii. p. 221, July 9, 1903), and the part now published completes the Cynipides, 5e tribu, Figitinæ; and also includes the Evaniides (divided into two tribes, Evaniina and Gasteruptioninae), the Stephanides, Trigonalides, Agriotypides, general supplements, a Catalogue méthodique et synonymique,' extending from pp. 653 to 741 (double columns), and general indices.

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The plan of the work is uniform throughout, and as the previous portions have already been discussed at considerable length, an extended notice is here W. F. K.

unnecessary.

The Gum-Bichromate Richards. Pp. 119.

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Ltd., n.d.) Price 2s. 6d. net. THIS process of photographic printing is about fifty years old, but it is only during the last ten years or so that it has been adopted for practical purposes. When first introduced it was deliberately rejected, because it was not equal to the then known processes in reproducing the detail of the negative; latterly it has been taken up and very much appreciated by some of those who desire to be able to alter or "control" their photographic printing, and so obtain results that, while they can lay no claim to mechanical accuracy, more nearly please the aesthetic taste of the worker. At the present time there are more methods of photographic printing than there were a generation ago that are excellently adapted for the purposes of photography pure and simple; therefore the gum-bichromate process is still more than it was then a process for the specialist in the direction named. The author of this volume is well known as a successful worker of the method. He gives his own formulæ, and states clearly the practical details that he prefers to follow, but he also describes the methods of others. He is a warm advocate of "multiple printing"; that is, after coating the paper, exposing, developing with warm water aided with a brush or by other mechanical means, coating, exposing, and developing a second or even a third or more times, so gradually building up the picture with the maximum opportunity of "control.” It will be obvious that every possibility of improvement in the hands of the skilful is a probability of error in the hands of the artistically ignorant, and that the process does not claim attention from a photographic point of view at all, but as enabling an artist to express his ideas with less trouble and perhaps with more accurate drawing than if he worked wholly by hand. The volume includes several reproductions of the author's works, some of them showing the print in its various stages of evolution.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Recent Changes in Vesuvius.

I BEG to enclose a somewhat free translation of a letter I have recently received from Prof. G. Mercalli, of Naples, concerning certain changes which have taken place in Vesuvius this year. During a visit to the mountain on August 14-16, I was able to approach quite near to the sources of the lava streams described by him, and also to examine the remarkable tunnels formed at certain places by the cooled surface of lava streams which had subsequently diminished in volume, or had even run dry.

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During the week preceding my visit, many incandescent bombs of pasty rock had been ejected from the crater at the summit, mostly in the direction of the side facing Pompeii, and these successively rolling down the ash-slope presented a beautiful spectacle at times. The lava streams proper often presented that curious double appearance, due to the fact that the colder and darker scoriæ, floating down the stream, keep to the more swiftly-moving current in mid-stream, and avoid the sides.

Yesternight (August 20) but one of the lava streams referred to by Prof. Mercalli was visible from Naples, the other having apparently ceased.

The explosions of Stromboli are occurring at intervals of about 3 minutes. R. T. GÜNTHER.

R.M.S. Oroya, off Stromboli, August 21.

Lava Stream of May 27, 1905.

IN the months of April and May of this year Vesuvius began to show an increased activity, and in the crater, which was about 80 metres in depth, a small cone began to form; it increased rapidly, and by the middle of May had risen to a height of about 15 metres above the level of the enclosing crater.

From May 25 to May 27 violent explosions occurred, which were heard in all the villages on the mountain-side,

FIG. 1.-Source of lava stream of August 26, 1003. From a photograph by Prof. G. Mercal i, taken April 15, 1904.

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and were accompanied by the ejection of much red-hot and liquid matter. These explosions ceased almost suddenly on the evening of May 27, and at about 6.45. a small lateral outlet, A," burst through the north-west flank of the great cone at a height of about 1245 metres, and at the point where a seam in the mountain-side showed where the traces of the last eruption of August 26, 1903, still lingered.

A few hours after the first, a second outlet was formed, then a third, "B, both lower down, at an altitude of

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FIG. 2.-Vesuvius as seen rom the Observatory Ridge, May 29, 1905. From a photograph by Prof. G. Mercalli.

lava piled itself up in the space between the cone and the hill formed by the lava-flow of 1895; a stream branched off, first toward Mount Somma, but afterwards in a southsouth-west direction, and a small stream more fluid than the main body ran to within a short distance of the electric railway which plies between the observatory and the lower funicular station. Near the fumarole "B" a small heap of scoriæ (a driblet-cone), about 4-5 metres in height, has sprung up; but apart from the explosions attendant on its formation, and which only lasted a few days, there has been no disturbance in the regular flow of the great

streams.

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The line of white steam seen in Fig. 2 shows the position of the outlets and the course of the lava streams seen from the observatory ridge; the black smoke issuing from the crater indicates the cloud of nonincandescent dust which was cast up after the partial falling in of the walls of the smaller cone on the summit.

We may perhaps attribute the frequency in these latter years of the lava streams from lateral outlets to the increased height of Vesuvius (now about 1330 metres), for the column of fluid lava, when inside the cone, is forced up to a higher level and exerts greater hydrostatic pressure on the sides of it, which are, moreover, much seamed. Formerly, when the mountain was lower, as, for instance, between the years 1840 and 1850, the lava streams generally flowed from the top.

The Millport Marine Station

SINCE the efficiency of such an institution as a biological station is so largely dependent upon the completeness of its library, I do not think any apology need be offered for appealing to those readers of NATURE who are interested in marine biology for assistance in an endeavour to bring together for the use of those working at the Millport Marine Station as complete a collection as may be possible of works having any bearing on the fauna and flora of the European seas. The station already possesses a considerable proportion of the more important monographs, as well as a number of useful pamphlets; but there are still lacking many reference works of importance, and I sure that copies of some of these will exist among the duplicates in many a naturalist's library. I would also urge the claims of the Millport Station upon the generosity of authors for separate copies of any papers they may publish; and in this connection it should be noted that the council of the association has recently agreed that all material intended for private research shall be supplied absolutely free of charge.

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This occasion may also be utilised to point out some of the advantages which the Millport Marine Station offers to the research student. The fauna of the Clyde area is an extremely rich one, and the water in the vicinity of the station is of most remarkable purity, so that even quite delicate species can be readily kept alive in the tanks. A small steamer, the Mermaid, specially built for scientific research, is constantly at work during the summer months, and brings in daily an abundant supply of material. The tank-room, only part of which is open to the public, has recently been greatly extended, and now has facilities which are probably unsurpassed anywhere for the accommodation of invertebrates and the smaller vertebrates; the tanks are mostly of glazed fire-clay, and capitally adapted for observation and experiment. Besides a well-equipped private research room, there are seven screened compartments in the general laboratory affording ample accommodation for nine students, while a large class-room recently added has benches for forty-five students.

The station is lavishly equipped with apparatus of all kinds-for instance, the student will find here every facility for advanced physiological work. In fine. I think it mas

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about 1180 metres, and both westward of the first, and fairly be claimed that nowhere in the British Isles will nearer the station of the funicular railway.

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the student find facilities for research on marine biolog such as exist at Millport; and, indeed, I know of no marine station elsewhere which can, all things considered offer greater advantages to the biologist. Lastly, it may be mentioned that although the fees are very low, there is never any difficulty in arranging for a free table. S. PACE (Director).

Millport Marine Station, N.B.

THE TOTAL SOLAR ECLIPSE, AUGUST 30. (1) THE SOLAR PHYSICS OBSERVATORY EXPEDITION. Palma, August 26. N another four days the eclipse will be an event packing up

great amount of material which we have been setting

have been previously calculated, give us 16 seconds and 5 seconds respectively before the commencement of totality. The object of employing these times is not so much to assist the observers in the camp generally, as to warn the workers with the prismatic cameras, who begin making their exposures three seconds before the commencement of totality. Both

FIG. 1. Our camping ground as seen from the south-east end. n the long tent on the left is the 76 ft. prismatic reflector, and all the other instruments are beyond it. Notice the poles for the discs in the right-hand corner.

The greatest party told off everyone will

up with so much care since August 11. keenness has been displayed in every for its particular duty, and I think that be glad when the eventful day arrives. We have settled down to routine work every day. Those in charge of instruments go to the camp at about 6.15, and work at the adjustments and small items SO necessary for successful photographs. At nine o'clock the whole band of volunteers, now about 150 in number, arrives at the camp, and three drills are then gone through in fairly quick succession. The organisation of the division of labour at each instrument is now very satisfactory, and the various movements that have to be stated performed at times Occur fashion. As I have mentioned before, the whole work of the camp is organised according to signals given by the

Mr. Butler and myself utilise these two signals to begin our series of snap-shots for photographing the lower chromosphere.

Undoubtedly the three minutes three seconds, the length of totality at this station, is a long time, and when the strong voices of the timekeepers are heard shouting out 163 seconds," "153 seconds more, &c., one somehow feels that one is not utilising to the fullest extent the time available.

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With the prismatic camera, of which I am in charge, it is hoped to secure fourteen photographs. The three large 6-inch prisms of 60°, and the object-glass of the same diameter, form together a powerful weapon of research. The programme of work is to make

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FIG. 2.-The camp as seen from the south-west end of the ground. The 3-inch McClean equatorial' in the foreground, 16 ft. coronagraph under tent on left, 76 ft. prismatic reflector under canvas on the right. All these instruments are housed with sails and spars from H. M.S. Venus.

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FIG 3.-The north end of the 76 ft. prismatic reflector, showing the dark room with the wine-tub for water, the two handcarts loaned us, and on the right, under the small awning, the 3-prism 6-inch prismatic

camera.

eclipse clock. There are, however, two further signals given from the angles subtended by the cusp at the centre of the dark room. These angles, which

four snap-shots at about the commencement of totality and five about the end. The remaining five plates will be exposed for intervals varying from 5 to 90 seconds, and it is hoped that the two long exposures on each side of mid-totality will add to our knowledge of the wave-lengths of the coronal rings. This prismatic camera is designed to give results suitable for determining accurate wave-length of the chromospheric and corona arcs; the image of the sun is therefore small, and the dispersion large.

The prismatic reflector of 76 feet focal length, in charge of Mr. Butler, provides a solar image of about 8 inches diameter, and, since the light is made to pass through one prism twice, the dispersion is not excessive. The large chromospheric arcs should, however, provide us with much matter for thought.

This latter instrument is practically ready for the eclipse, and a few words may here be said as regards the erection of it. The camera end itself forms part of the dark room of the camp, and is to the south of it. Just outside, but a little to the west of the north and south line, is the siderostat, which throws the solar rays on to the long-focus mirror situated to the south about 70 feet. This concave reflector throws the image towards the north, into the portion of the dark room in which is fitted a Screen. An arrangement is adopted for inserting, during some periods of totality, a prism in front of the mirror. The light from the siderostat has thus to pass twice through the prism, giving a very useful

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had to spend the whole of Saturday, August 26, in bed by the doctor's orders; but my instrument was very efficiently worked by the navigating officer, Lieut. Horne, who will make the cusp observations from my siderostat during the eclipse. In each party, then, the work of each member was changed, and drills were carried out under this scheme with success. I should like to take this opportunity of thanking

most heartily both Staff-Surgeon Clift and Surgeon Jones, of H.M.S. Venus, for their very kind and efficient assistance on that occasion.

The camp at the present time practically fills the whole of the enclosed ground placed very generously at our service. Through the kindness of the local authorities, extra tents have been provided, and much material loaned in the way of wood for the shadowband party, handcarts for the use of the men bringing water and provisions from the ship, &c.

To avoid the inconvenience of any dust arising from the road to the north of the camp, the same authorities will keep this well watered on the day of the eclipse, and for some days previous to it, and they have also arranged that the manufacturers' chimneys, which are very numerous here, shall not smoke during the time of the eclipse.

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WILLIAM J. S. LOCKYER.

(2) REPORTS OF OBSERVATIONS.

Up to the time of writing very few details as to the actual scientific results obtained during the total eclipse of the sun on August 30 have arrived in this country; but it is very clear that the hopes expressed in these pages on August 24 have not been completely realised on account of the prevalence of cloud during totality at several stations.

Telegraphing from Castellon, Prof. Callendar states that, although the first and last contacts were observed in a clear sky, totality was entirely obscured by clouds. Good records of radiation and temperature were, however, secured. Similarly, Mr. Evershed, who had set up a very fine prismatic camera near to Burgos, says in a telegram to the Royal Society, "Thick clouds; no results." This forms a striking contrast to the reports of the Press correspondents, which state that all the observations at Burgos itself were successfully carried out during a temporary break in the clouds. A reproduction of a photograph of the corona, taken with a camera of 48 inches focal length by Mr. J. T. Pigg at Burgos, appeared in the Daily News for September 2.

At Palma, Majorca, the expedition from the Solar Physics Observatory, South Kensington, under the direction of Sir Norman Lockyer, and assisted by the officers and crew of H.M.S. Venus, were apparently only a little more successful, for as the crucial moment of totality arrived dense clouds came up and obliterated the sun. At about mid-totality, however, a break in the clouds occurred, and some photographs were secured which, it is hoped, may at least show the form and extent of the corona. Several good drawings of this feature, which was of the "maximum" type seen in 1871 and 1882. were made by the "disc" sketching parties.

At Saragossa, cirrus clouds prevented observations being made.

Encouraging but brief reports have been received from the observers at the North African stations.

Mr. Newall, at Guelma, appears to have been singularly fortunate, for he reports "superb weather conditions, observations successfully made," and states that he observed a brilliant corona of the "maximum" type having remarkably long streamers

one of which extended towards Mercury for more than three degrees and unusually dark rays. Splendid prominences were also observed by him.

Sir William Christie's report from Sfax is not quite so sanguine, for he states that the sky was partially cloudy; nevertheless, photographs were secured with all instruments, and the eclipse was satisfactorily observed. A Reuter telegram from this station says that during the period of totality no clouds interfered with the observations.

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At Assuan, where Prof. Turner set up his coronagraph and polariscopic apparatus, the atmospheric conditions were perfect, except for a slight haze, and the Times correspondent reports that eight photographs in polarised light were obtained and successful corona pictures were taken. Mr. Reynolds with his 120-feet reflector evidently experienced the great drawback common to all users of long-focus cameras, viz. bad atmospheric tremors, for the local fire brigade had to be requisitioned to flood the site in order to check the radiation from the heated ground.

Dr. J. Larmor sends us the following observations made by Mr. S. L. Walkden on the Orient steamer Ortona, situated on the central line of the eclipse in the Mediterranean near the Spanish coast. The observations contain a good naked-eye record of the eclipse, and agree with Dr. Larmor's impressions :— Rainbow colours visible on small cloud about 5° from sun about minute to 1 minute before totality. Pulsation of light from strip of sun was observed by Mr. Campbell and myself as if the moon advanced by stages. (Probably another aspect of shadow-bands phenomenon.) No approach of shadow observed by myself, though keenly looked for; but found no one else who observed it except Mr. Campbell, who caught it in the sky not far from sun's limb at time of approach of totality. Totality.-Venus first noticed about one minute before totality, and Regulus as soon as totality complete. Mercury searched for with Zeiss field-glass and naked eye, but not caught after about 10 to 15 seconds' search. Corona.-Very fine and very detailed, so that general description difficult. General impressions. (1) Some streamers seemed to cross, and were certainly not all radial. (2) Obvious extension seemed about two sun diameters. (3) Streamers distributed all round sun, but chiefly at left-top (45° from top) limb. Long thin streamer at left-leftbottom limb (671° to left of bottom). Prominences.Distributed more or less all round, but chief one observed at left-top corner. Height about sun's radius; but this should be corrected for irradiation, which made the prominence appear to trespass into the moon's surface, exaggerating its size and producing general local glare. Colour of prominence was much less marked than expected, being merely of a violet or faintly rosy-pink hue. Shadow bands observed on deck at end of totality (looking down from boat deck). They rippled along a little faster than could be easily followed by eye. They were parallel to the strip of the sun after totality, and travelled in direction of shadow. Dark strips about 6 to 8 inches wide, distance apart about 18 inches. During totality depth of darkness seemed practically independent of depth of our immersion in shadow. Clouds formed a good deal after of sun's diameter had gone. Lightness of eclipse very marked, and in itself disappointing. Time by watch always plainly visible. Sky illumination greatest round horizon, and a vellow glow (like sunset) in points opposite to sun (about N. point). Coast lights were visible a few miles away, and one hill to N. appeared as if perforated, with the sky showing through. This was observed by one other passenger. Venus still visible nearly minutes after end of totality. Whole black disc of moon was visible shortly before totality, say 5 to 10 seconds before.

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According to a correspondent writing to the Times, some interesting observations of a simple character were made by the amateur astronomers on board the P. and O. mail steamer Arcadia, which for the time of the eclipse waited off the coast of Spain not far from Castellon. Members of the British Astronomical Association were on board, and organised themselves to watch various features of the phenomena. Mr. and Mrs. Johnson report that they saw the whole

contour of the moon projected on the corona immediately after the first contact. Thermometric observations showed a fall from 90° to 72°.6 in the sun, and from 82°.4 to 72°.5 in the shade, temperature. Mr. Bacon, first officer of the Arcadia, made successful observations of the approach and of the recession of the moon's shadow from a point of vantage at the mast-head.

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As regards the observations made by foreign astronomers, those located at Castellon, Burgos, Guelma, Sfax, and Assuan shared, of course, in the conditions enumerated above. M. Trépied, of the Algiers Observatory, was apparently very successful Guelma, and obtained numerous photographs of the chromospheric spectrum and the corona. A fall of temperature of 5° C. (from 33° to 28°) was recorded, and Mercury, Venus, and Regulus were observed.

At Tripoli, Prof. Todd, of Amherst College Observatory, M. Liberd, of Paris, and Prof. Millosevich, of Rome, were favoured with a clear sky. Prof. Todd secured some 250 photographs of the corona with his automatic coronagraph. Very good observations of the shadow-bands are said to have been made at this station.

A disappointing feature of the eclipse was the failure to secure observations at both ends of the shadow's path. As mentioned before in these columns, arrangements had been made by the Lick Observatory to photograph the corona in Labrador and in Egypt with exactly similar coronagraphs. Mrs. Maunder, accompanying the Canadian party at Hamilton Inlet (Labrador), was also to use a coronagraph identical in scale with that used by Prof. Turner at Assuan. A Reuter telegram from St. John's, Newfoundland, announces, however, that the Lick observers experienced a total failure owing to clouds; a second message from a telegraph station on Hamilton Inlet stated that fine weather prevailed from 7 a.m. to 6 p.m. on the day of the eclipse, and that the phenomena were perfectly visible, and it was hoped that the Canadian party had been successful in making good observations. A later telegram, dated September 3, states, however, that the expedition was entirely unsuccessful, owing to the cloudy weather, and no photographs were secured.

A communication from Mr. J. Y. Buchanan, F.R.S., to the Times of September 5, contains some interesting notes of visual observations made during the period of totality at Torreblanca, a small village on the east coast of Spain. Having been present at the 1882 eclipse, when he assisted Sir Norman Lockyer at Sohag, on the Nile, and not having seen the whole of the phenomena, Mr. Buchanan only took with him an ordinary camera and a field-glass, so that he might devote all his attention to visual observations. His choice of Torreblanca, where, with the exception of the local railway employees, he seems to have been the sole observer, was justified, inasmuch as the eclipse took place in a blue sky. As the last vestige of sun disappeared behind the eastern limb of the moon a magnificent bunch of prominences, of a light violet hue, appeared at the same part of the limb; but these subsequently disappeared, and a careful search at mid-totality failed to reveal any prominences at all. A similar group, however, burst into view on the opposite limb just before the end of totality, thus indicating that the apparent diameter of the moon was sufficient to cover the whole of the prominence layer of the sun's limb at mid-totality.

The corona was clearly visible near to the western part of the moon's limb eight seconds before the advent of totality, and throughout totality it was very clearly defined. On an average it extended to rather more than one lunar diameter from the limb, but a streamer on the lower western limb was judged

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