April 26, 1877] 



NATURE 



563 





the issue of this handsome work by the private energy of one of 

 its members. — Sir Chas. Strickland exhibited a specimen of 

 Crimtm aquaticum obtained from Grahamstown, South Afiica, 

 biit which showy plant hitherto has rarely been seen in flower in 

 Britain. — A paper on ferns collected by Miss Gilpin in the inte- 

 rior of Madagascar, was read by Mr. J. G. Baker. vSome seven- 

 teen are new out of 150 species, a fair proportion, and evidence 

 of an unsuspected richness in this department of the Madagascar 

 flora. — The vSecretary announced a paper on the fresh-water 

 algoe of the Cape of Good Hope, by Prof. Reinsch : this being 

 of a technical character, and in Latin, was taken as read. — Mr. 

 R. CoUett, of Christiania, then read a communication on 

 Myodes levimus in Norway. His observations on the habits and 

 economy of the Lemming had extended over several years, and 

 in 1876 he had published these in Nyt. Ma^. f. Naturi'sk. 

 But his attention had lately been called to Mr. Crotch's contri- 

 butions in the Linnean Journal, and as in many particulars he 

 differed from that author, the present notice resulted. The num- 

 ber of young at a birth vary from three to eight, and two sets 

 are annually produced. Mr. CoUett regards their wandering as 

 a necessary consequence of their temporarily strong vitality, 

 together with an inherent migratory instinct. The tendency at 

 intervals to appear in unusually large numbers is not confined to 

 the genus, but is common to all the species of the sub-family 

 Arvicolinge. The majority of the wanderers are young, and in one 

 instance observed, by himself, were chiefly males. The migration 

 closes with the death of the individuals, generally brought about 

 by an epizootic disease, the result of over population ; tl^ denser 

 the masses the higher the rate of mortality. The bare pitch on 

 the rump considered by Mr. Crotch to be due to the habit of pro- 

 tecting themselves against stones in resisting attack, Mr. Collett 

 states is due to a skin disease. He however, supports Mr. 

 Crotch's statement as to the number of winged and four-footed 

 enemies which devour the Lemming, and also that domestic 

 cattle and reindeer destroy them. Their occasional enormous 

 increase in numbers he holds to be owing to periodic prolific 

 years, the facility of rearing their young, and the early pro- 

 creative faculty of the latter. Parallel instances among other groups 

 of animals, for instance unusual swarms of butterflies and locusts 

 are well known, though as to the true reason of such departures 

 in number, &c., much is only conjectural. Coincidently with 

 the notable years of the Lemming migrations, the increase above 

 the normal number of rats, mice, shrews, and even the grouse 

 tribe, have been recorded. Mr. Collett affirms that the Lemmings 

 travel chiefly in the direction of the valleys, and not constantly 

 due west as has been asserted ; their great movements are chiefly 

 nocturnal. He is inclined to question Mr. Crotch's notion of here- 

 ditary search for a " Miocene Atlantis," and rather is of opinion 

 that in accounting for the periodical excess of multiplication and 

 migratory impulse a physiological necessity impels them ; the 

 nature of this is at present beyond our power to explain rationally, 

 —A further contribution to the natural history of swine, by Prof. 

 RoUeston, was read in abstract, this paper forming an appendix 

 to that previously brought under the notice of the Society. The 

 additional information is in the main confirmatory of the views 

 already expressed, but several important facts relative to the 

 striping of the young of Sus ceUbensis and .S'. verrucosus according 

 to Dr. A. B. Meyer, with information from others, necessarily 

 causes a modification in former conclusions. — On South African 

 Hepaticse (Liverworts), by Mr. W. Mitten, and on new Irish 

 Lichens, by the Rev. W. A. Leighton, were two technical 

 papers the titles only of which were read by the Secretary. 



Royal Astronomical Society, April 13, Dr. Huggins, 

 F.R.S., president, in the chair. — Lord Lindsay read a paper on 

 the diurnal parallax of Juno observed at Mauritius in 1874 with 

 the heliometer, which (rejecting one discordant observation) gave 

 a value of 8" '82 for the solar parallax.— Mr. Gill read a paper 

 on the proposed expedition to observe the approaching oppo- 

 sition of Mars. Observations can be made during six weeks. 

 At the Island of Ascension the geometrical conditions are about 

 as favourable as possible ; and what is of great importance, the 

 meteorological conditions are no less so, the range of tempe- 

 rature between 6 p.m. and 6 a. m being only two or three 

 degrees. None of the stars of comparison are of less than the 

 eighth magnitude, and they are selected so as to determine the 

 position of the planet in right ascension as accurately as possi- 

 ble. Mr. Gill proposes also to observe the oppositions of the 

 minor planets Ariadne, Iris, and Melpomene That of Ariadne 

 occurs ten days earlier than Mars. Its declination will be 15 

 south. Melpomene has 2° north declination.— Mr. Christie 



explained the principle of his new form of spectroscope. It 

 depends on the fact that the half of an isosceles prism, cut per- 

 pendicular to the base, magnifies the angle between two incident 

 pencils, by virtue of the oblique emergence. I5y using a com- 

 pound prism composed of a half prism of flint with a prism of 

 crown cemented to the oblique face, to correct the deviation, 

 the magnifying effect might be increased to ten or fifteen times. 

 By turning the half-prism about its centre different parts of the 

 spectrum would be brought into the field without any movement 

 of the viewing telescope. With two half-prisms the dispersion 

 of ten ordinary compound prisms has been obtained, and with 

 better definition ; for with ten prisms the errors of forty surfaces 

 are accumulated. When the breadth of the lines is diminished 

 by narrowing the slit, the spectrum is still far brighter than in 

 the other form, for the loss by absorption is enormous, amounting 

 to 50 per cent for three or four inches of glass, and in the large 

 Greenwich spectroscope only j^th part of the incident light 

 reaches the eye. Mr. Bidder, Lord Lindsay, and Mr. Gill 

 offered some criticisms, and Mr. Christie replied, showing that 

 he had anticipated all the objections offered. — Prof. Pritchard 

 read a paper on the comets of '1877. The recent dearth of 

 comets he attributed to the probable sleepiness of seekers. Two 

 had been obseived at Oxford, and the elements and an ephemeris 

 of Winnecke's calculated. They had made objcrvations on April 

 7 and 1 1, which were combined with Prof. Winnecke's of the 

 5h. in making the calculations. — Prof. Pritchard also read a 

 paper on a mechanical solution of Kepler's problem. — Mr. J. 

 W. L. Glaisher read a paper on an elliptic-function solution of 

 Kepler's problem. — The Rev, S. J. Perry described how 

 neither he nor his assistants could see Vulcan. — Lord Lindsay 

 stated that M. Leverrier thought it would be useless to look for 

 Vulcan for the next six years. 



Mathematical Society, April 12. — Lord Rayleigh, F.R.S., 

 president, in the chair. — Mr. C. Pendlebury was elected a mem- 

 ber. — The following communications were made : — On Hesse's 

 ternary operator and applications, by Mr. J. J. Walker. — 

 Geometrical illustration of a theorem relating to an irrational • 

 function of an imaginary variable, and on the general differential 



d X dy 

 equation ~t^ + ~i^= o, where X, Y are the same quartic func- 

 tions of X, y, respectively, by Prof. Cayley, F.R.S. (Profs. Smith 

 and Henrici look part in a discussion on these papers, the former 

 making remarks on the question whether infinity is a point or 

 a straight line). — Mr. Merrifield, F. R.S., vice-president, having 

 taken the chair, Mr. Harry Hart deduced some cases of parallel 

 motion from the consideration that the contra parallelogram 

 represents the motion of two equal ellipses rolling upon each 

 other, and that of these (i. ^., parallel motions) two especially were 

 very simple, inasmuch as the motion was obtained in either case 

 by the use of five bars only and was moreover perfectly con- 

 tinuous. — Mr. Tucker, hon. sec, read an abstract of a paper 

 by Prof. H. W. Lloyd Tanner, on a method of solving partial 

 differential equations which have a general first integral, applied 

 to equations of the third order with two independent variables. 



Chemical Society, April 19. — Dr. Gladstone in the chaii. 

 — The following papers were read : — On the estimation of man- 

 ganese in spiegeleisen, and of manganese and iron in manganl- 

 lerous iron ores, by E. Riley. For estimating manganese in 

 spiegeleisen the author recommends the indirect method, i.e., 

 estimating the iron, adding five per cent, for impurities, and 

 taking the ditference as manganese, for accuracy and rapidity ; 

 for the estimation of manganese in its ores the author prefers to 

 separate the iron as basic peracetate with carbonate and acetate 

 of ammonia, and to precipitate the manganese with bromine 

 and ammonia, taking care that the ignited precipitate contains 

 no baryta, zinc, or lime. For the determination of the iron a 

 standard solution of bichromate of potash yields the best results, 

 the iron being reduced with pure sulphite of soda. — On a method 

 of detecting small quantities of bismuth, by M. M. Pattison 

 Muir. The author proposes Schneider's reagent, consisting of a 

 clear solution of 1 2 grm. of tartaric acid and 4 grm. stannous 

 chloride in caustic potash ; one part of bismuth in 210,000, if 

 warmed to 60°- 70° C. with this reagent, gives a brownish colour. 

 —On certain bismuth compounds, by M. M. Pattison Muir. 

 This paper gives an account of the properties and reactions of 

 bismuth ferricyanide. — Notes on madder colouring matters, by 

 E. Schunck and H. Roemer. Munjistin : this substance re- 

 sembles purpuroxanthic acid in its physical properties. Pur- 

 purin : a pure specimen was examined, and its properties are 



