December io, 1891] 



NATURE 



H3 



of the drop freezing as the liquid state progressed. Many 

 points raised in the paper were, he said, very interesting, and 

 the suggestion that the discrete nature of atoms is the result of 

 the coarse-grainedness of matter, very good. On the other 

 hand, he considered the static treatment of strain-figures im- 

 proper, for the ultimate conditions must be kinetic. Dr. O. 

 Lodge agreed with Prof. Fitzgerald in regarding the motion of 

 the loop along the rope as a wave motion whose velocity of 

 propagation is equal to that of the loop. A similar case occurs 

 when a ring of rope is spinning, and has a pulse impressed on it 

 at one point, for the pulse travels at the same speed as the rope. 

 —A paper on a permanent magnetic field, by Mr. W. Hibbert, 

 was postponed until next meeting. 



Royal Microscopical Society, November i8.— Dr. R. 

 Braithwaite, President, in the chair. — A special meeting was first 

 held, at which certain alterations in the by-laws were proposed by 

 the Council, and accepted by the Fellows. The ordinary meeting 

 was then constituted.— Mr. C. L. Curties exhibited and described a 

 small heliostat made on the lines laid down by Mr. Comber. It was 

 simple and effective, and was adapted for use in any latitude 

 between 15° and 70°.— Mr. J. W. Gifford read a paper on the 

 x^%o\\x\\ovioi A mphipleura pellucida. Mr. Gifford said he had 

 examined a frustule of ^./,?//««'a'(2 with sodium light illumina- 

 tion, that being the most convenient form of monochromatic 

 light at the time. Under this light A. pellucida unmistakably 

 showed dots, which became more marked as the frustule was 

 shifted to the side of the field of vision. The question then 

 arose as to the possibility of photographing the object by the 

 light of the sodium flame, and plates treated with an erythrosine 

 bath were used. It occurred to him that a trough containing a 

 solution of iron perchloride used as a screen would cut off all the 

 blue end of the spectrum, and also some of the green, leaving 

 only the green yellow, yellow and red ; but on the other hand, 

 he found the erythrosine plates were only sensitive as far down as 

 the yellow, more especially to the green-yellow. In this way 

 the part of the spectrum used for photographing could be 

 reduced to a narrow band about midway between the D and E 

 lines in the solar spectrum. By this means he succeeded in 

 obtaining the photographs exhibited, and which he had avoided 

 touching up. Whether these markings were true or spurious was 

 a question he did not touch, but they appeared to have as good 

 a claim as those on Stirirella gemma. He thought it more 

 probable that in both cases they were simply multiplied rings of 

 the midrib and sides produced by the higher order of diffrac- 

 tion spectra according to the Abbe theory. The mounts of 

 A. pellucida used were of realgar, or rather a higher sulphide of 

 arsenic, prepared by mixing sulphur with realgar. He found it 

 extremely difficult to make mounts with such a large proportion 

 of realgar. The mounts being of a deep orange colour inclining 

 to red, enabled the coloured screen to be dispensed with. But 

 this highly refracting medium very soon cracks off the cover- 

 glass. The advantage of working with this form of illumination 

 and a suitable colour-correct plate is that ordinary achromatic 

 object-glasses perform almost as well as apochromatic. He could 

 not see the beaded markings with any glass of less aperture than 

 l'4 ; the best results being obtained with Powell and Lealand's 

 apochromatic ^^ of I '5, also with their achromatics ^V of i'5 and 

 ,'7 of I '43. He also used in photographing a Zeiss projection 

 ocular. — Mr. E. M. Nelson, speaking of the value of drawings 

 made with Beale's neutral tint reflector, said he had tested the 

 matter by making a drawing of lines on a micrometer scale of 

 ^^jr mm. under an apochromatic objective giving a magnifying 

 power X 850 ; he found on measuring that they showed only a 

 very slight displacement. — Mr. Curties exhibited a new form of 

 microscope made on the Nelson model. — Mr. Nelson described 

 some improvements in his apparatus for producing pure mono- 

 chromatic light for use with the microscope. — Mr. A. W. Bennett 

 gave a ;-/5«OTt^ of his paper on the fresh- water Algae of South- 

 west Surrey, in which he describes several new species. 



Cambridge. 

 Philosophical Society, November 9. —Dr. Gaskell in the 

 chair. — The following communications were made: — On a 

 Peripatus from Natal, by Mr. A. Sedgwick. — On variations 

 in the colour of cocoons {Sattirnia carpini and Eriogaster 

 laneslris), with reference to recent theories of protective colora- 

 tion, by Mr. W. Bateson. The cocoons of several moths, e.g. 

 the emperor and small egger, vary in colour from dark brown to 

 white. It is believed by some that these colours have a 

 protective value as a means of concealment, and [it has been 



NO. 1154, VOL. 45] 



stated by Poulton and others that when spun on leaves which 

 will turn brown, or in dark surroundings, the cocoons are dark, 

 while they are white if spun on white paper. To account for 

 this phenomenon "the existence of a complex nervous circle " 

 has been assumed. The present experiments showed that it is 

 true that larvae left to spin on their food-leaves produce dark 



\ cocoons, and also that if they are taken out and put in white 



I paper the cocoons are white. But it was found that larva 

 similarly /a/^^« out and made to spin in dark substances also 

 spun white cocoons, and indeed that starvation, parasites, or 

 interference at the time of spinning, lead to the production of a 

 white cocoon. On the contrary, if white paper is put amongst 

 the food, so that the larvae can, of their own choice, walk into 

 it and spin, the cocoons are generally dark. It was noticed 

 in several cases that larvae which had been shut up evacuated a 

 quantity of dark juice having the natural tint of the cocoon, and 

 the suggestion was hazarded that absence of colour in the cocoon 

 perhaps results from the loss or retention of this juice, which 



; may be of the nature of meconium. — Exhibition of Phylloxera 

 vastatrix, by Mr. A. E. Shipley.— On digestion in Ammoccetes, 



j by Miss R. Alcock (communicated by Dr. Gaskell).— On the 

 reaction of certain living cells to methylene-blue, by W. B. 

 Hardy.— The chair was taken by Prof. Hughes during the 

 reading of the last two papers. 



Paris. 

 Academy of Sciences, November 30. — M. Duchartre in 

 the chair. — The reclaiming and cultivation of land in tha 

 Camargue, by M. Chambrelent. A description of the irrigation, 

 cultivation, procuring of potable waters, and means of transpor, 

 introduced in the Camargue. This district is contained between 

 two branches of the Rhone, 50 and 58 kilometre? long re- 

 spectively, which reach the sea at points about 40 kilometres 

 from each other. The bifurcation occurs at Aries, about 50 kilo- 

 metres from the coast. At the beginning of this century the land 

 was absolutely unfertile, and the inhabitants were unprovided 

 with potable water. The author states the success that has 

 attended the efforts that have been made to remedy this state of 

 things, and bring the land under cultivation.— Observations of 

 the asteroid discovered by M. Borrelly, at Marseilles Obser- 

 vatory, on November 27, 1891, by M. Borrelly. The positions 

 are given for November 27 and 28. — Rhume of solar observa- 

 tions made at the Royal Observatory of the Roman College, 

 during the third:quarter of 1891, by M. P. Tacchini. (See 'Our 

 Astronomical Column.) — On the tides of the Bay of St. Malo, 

 by M. Heurtault. The author has made tidal observations at 

 St. Malo for the last eighteen years, and states some of the 

 results. The mean monthly level of the sea appears to have a 

 minimum value in April and a maximum in October. The 

 mean annual level increased gradually from 1874 to 1883, and 

 has since been diminishing. The establishment of the port also 

 indicates similar variations. Thus it passed from 6h. 55m. 

 in 1874 to 6h. io-24m. in 1884, and has since exhibited a 

 tendency to diminish. Its months of maxima are April and 

 September, and of minima July and December, the general mean 

 being 6h. 8-9m. Contrary to Laplace's statement—" Flus la 

 mer s'eltve lorsqu'elle est pleine, plus elle descende en basse mer 

 suivante " — it has been found from observations of 45 tides, that 

 in only 25 did the lowest sea follow the highest tide ; 3 times it 

 immediately preceded, and 17 times it occurred two tides before. 

 — Phosphides of boron, by M. A. Besson. The preparation and 

 properties of boron phosphide, PB, are described ; the possible 

 existence of a more stable compound is also indicated. — On the 

 bromine derivatives of methyl chloride, by M. A. Besson. The 

 compounds CHaBrCl and CHBroCI have been prepared. The 

 author has not yet succeeded in isolating CBr^Cl. (l) The 

 compound CH2HrCl is a colourless liquid distilling without de- 

 composition at 4- 68°, solidifying at -55°; its specific gravity is 

 1*90. (2) CHBrjCl boils between 117"' and 119°, and solidifies 

 at - 32°. — On a modification of the calorimetric bomb of M. 

 Berthelot, and upon the industrial determination of the calorific 

 power of combustibles, by M. Pierre Mahler.— On the fixation 

 of free nitrogen by plants, by MM. Th. Schloesing, Jun., and 

 Em. Laurent. The conclusions drawn from the data obtained are 

 the following :— (i) There are some inferior green plants capable 

 of fixing gaseous nitrogen. (2) Under the conditions of experi- 

 ment peas take up much atmospheric nitrogen, whereas fallow 

 soils, oats, mustard, cress, andspurrey are not capable of fixing a 

 measurable quantity. The paper has remarks by M. Berthelot 

 appended. — The ammonia in the atmosphere and in the rain of 



