552 



NATURE 



[April 2,, 1886 



acids, by M. A. Ditte. Here the author deals with those oxy- 

 genated acids, such as sul|-)luiric, arsenic, iodic, &c., which may 

 be freely isolated under the form of crystals. Those hitherto 

 obtained only as salts are reserved for future consideration. — On 

 the products of decomposition of hypophosphoric acid, by M. A. 

 Joly. — Action of platina at a red heat on the fluorides of phos- 

 phorus, by M. H. Moissan. — On the decomposition by com- 

 pensation of compound bodies optically inactive, by M. E. 

 Bichat. — On a photo-chemical reaction of the oxymetric fluid of 

 M. .Schiitzenberger, by M. Victor Jodin. It is shown by re- 

 peated experiments thai the o.xyrnetric reagent is of itself sensi- 

 tive to light and that account should be taken of this property 

 in researches dealing with photo-chemical reactions accompanied 

 by a liberation of o.xygen. — On the volatile character of the oxy- 

 genated nitriles, by M. Louis Henry. — Note on the salivary 

 sylands in the order of Coleopter;^, by M. J. C?^zagnaire. A 

 chief result of the author's researches is the verification of the 

 hypothesis that salivary glands are developed throughout the 

 whole order of Coleopterce. — On the mode of formation of the 

 chromatophores in the Cephalopods, by M. C. Phisalix. — On 

 the toxic properties of the Cytisus, by M. Ch. Corneviu. Of ten 

 species of Cytisus two were found to be harmless (C. stssiliflonn 

 and C. capitatus), two slightly venomous (C nigricans and 

 C. sufiiiius), six extremely venomous (C. Lalnimttm, C. alfiims, 

 C. purfuicU!, C. WchUnii, C. biflorus, and C. elongatns). — 

 Note on the Paljeozoic formations of the Neffiez-Cabrieres dis- 

 trict, Herault, by M. de Rouville. 



Berlin 



Physical Society, Feliruary 5. —Dr. R. von Helmholtz, in 

 an investigation into the ten^ions of vapour of solutions of salt, 

 made use of a method whereby the least depressions under which 

 a condensation of vapour occurred, when no heat was admilled 

 from the outside, were determined. With this end in view a 

 glass cylinder was filled to a third of its capacity with the fluid. 

 The space filled with a mixture of air and vapour was on one 

 side connected with a manometer, while a second cock allowed 

 the depression to be effected, a small over-pressure having been 

 generated beforehand. The first formation of cloud was ren- 

 dered visible in this wise, that a bundle of light was directed', 

 through the axis of the glass cylinder, and the observer in a dark 

 section of space under small angle looked towards the axis. 

 Experiments with pure water showed that in saturated air the 

 depression needed first to attain a certain value before the 

 formation of cloud set in. Under the temperature of a sitting- 

 room this depression amounted to about 10 mm. water ; at o- a 

 depression of 12 mm. water was required. In this investigation 

 Heir von Helmholtz confirmed the statements of MM. Coulier 

 and Aitken, that the formation of cloud in saturated air was 

 induced solely by particles of du^t. Saturated air completely 

 free of dust might suffer a depression of half an atmosphere 

 without any cloud getting formed in it. The finer and sparser 

 were the dust-particles the slower was cloud in forming itself in 

 the vapour-saturated air. Salt-particles and acids furthered the 

 formation of cloud, and, most powerfully of all, particles of sal- 

 aijimoniac. An explanation of this phenomenon the speaker 

 found in the proposition demonstrated by Sir William Thomson, 

 that the tension of vapour was greater over convex than over 

 even surfaces of fluidity. When the air w.\s without dust- 

 particles there were wanting the convex surfaces at which 

 the tension was higher and it was possible for the precipitate to 

 ensue. Dust-particles, on the other hand, presented such 

 surfaces, and all the more the rougher they were. In the atmo- 

 sphere dust-particles must be present as far up as to the highest 

 layers in which clouds were formed, seeing that without them no 

 cloud-formation was possible. This circumstance yielded sup- 

 port to the explanation given by Prof Tyndall of the blue 

 colour of the sky, in accordance with which the sky was in- 

 debted for its blue colour to the particles floating in the air. 

 The dense and persistent fog-formations in large cities, such as 

 London, were caused by the sulphuric acid with which the air 

 was charged in consequence of the vast consumption of coal, 

 and which thus favoured the formation of clouds. The fact, 

 demonstrated by experiments, that saturated water vapour did 

 not, even under the lowest depression, give rise to the formation 

 of cloud, but required first to attain a perceptible magnitude, 

 rendered necessai'y a change in the theoretical formulae for the 

 conditions of cloud-formation. Determinations executed accord- 

 ing to this method of the tensions of vapour of various sulphuric 

 acid solutions showed a very good 'agreement with those exe- 



cuted by Regnault. — Dr. Frohlich gave a short report on the results 

 of his investigations, lasting for years, into the theory of the 

 dynamo-electrical machines, which he had developed with 

 special reference to the practical requirements of technics, and 

 had quite recently pub'ished in a separate work. He com- 

 municated and explained the concluding formulae he had found 

 for the performance of the various systems of machines, in 

 respect of their magnetism, as also of their intensity and polar 

 tensions. He likewise gave the formulae for the performances 

 of the dynamo machines as transmitters of energy. Be it here 

 specially brought out that, in contrast with MM. Deprez and 

 Silvanus Thompson, he hatl found that, for the mechanical per- 

 formance of two machine^ of similar construction and unequal 

 dimensions, the larger did not gain in mechanical labour to the 

 extent of k", n being used to denote the linear enlargement, 

 but only in the proportion of about «', in which the mass also 

 increased. The utility-effect, on the other hand, of a machine 

 of similar construction, increased with enlargement in the pro- 

 portion of n^. 



BOOKS RECEIVED 



" British Museum (Natural History) Mineral Department— An Introduc- 

 tion to the Study of Meteorites."—" Astronomical Observations 1882-85 

 made at Rousdon Obser\'atory," byC. E. Peek. — " Arithmetic for Schools," 

 by the Rev. J. B. Lock (Macmillan).— " Si.xteenth Annual Report of the 

 Wellington College Natural Science Society, 1S85" (Bish..p, Wellington).— 

 " Key to the Text-Book on the Mechanics of M.ii.-m (! , ^ ' !i\- M. Merri- 

 man (Wiley, New York).— " The Elements ol" I 1, i,, by H. 



D. MacLeod (Longmans). — "Watt's Organic riiiui.:,., , !,d by IVof. 



W. A. Tilden (Churchill).—" Bulletin of the Phiio ihi. ,: :- i.ty of Wash- 

 ington," vol. viii. (Washington). — "The Doctrine ot h,v 'lution in its Appli- 

 cation to Pathology," by Dr. W. Aitken (MacDoiigall. Glasgow). -"A 

 Manual of Mechanics," by T. M. Goodeve (Longmans). — "The Code of 

 Nomenclature and Check List of North American Birds " (American Orni- 

 thologists' Union, New York). 



CONTENTS p.\GE 



Kinship and Marriage in Early Arabia, lly Andrewr 



Lang 529 



Field's Chromatography 530 



Our Book Shelf:— 



" American Journal of Mathematics " 53' 



Scott's " Burma, as it was, as it is, and as it will be " 531 



Holder's " Marvels of Animal Life " 532 



Letters to the Editor :— 



Integer Numbers of the First Centenary, satisfying the 



Equation A^ = B- + C-.— Sir G. B. Airy, F.R.S. 532 

 The Sunrise Shadow of Adam's Peak, Ceylon. — Hon. 



Ralph Abercromby. {Illustrated) 532 



" Bishop's Ring." — Edward F. Taylor 533 



" Ferocity of Rats." — W. August Carter .... 533 

 Weather in South Australia. — Stevenson's Thermo- 

 meter-Screen. — Clement L. Wragge 533 



"Radicle" or "Radical." — H. G. Madan . . . 533 



An Earthquake Invention. — D. A. Stevenson . . 534 



Dr. T. Spencer Cobbold, F.R.S. , F.L.S 534 



The Geologists' Association at the Science Schools 534 

 Photographic Study of Stellar Spectra. By Edward 



C. Pickering 535 



Solar Halo with Parhelia. By William Ellis ... 535 



Notes 536 



Our Astronomical Column : — 



An Astronomical Directory 53^ 



Rousdon Observatory, Devon 53^ 



The Great Melbourne Telescope 53^ 



Astronomical Ptienomena for the Week 1886 



April II- 17 53S 



Geographical Notes 539 



The Saharunpur Botanical Gardens 539 



The Sun and Stars, V. By J. Norman Lockyer, 



F.R.S. (Illustrated) 540 



The Correlation of the Different Branches of 

 Elementary Mathematics. By R. B. Hayward, 



F.R.S 543 



On the Method of Stating Results of Water 

 Analyses. By A. C. Peale, M.D., Wm. H. Sea- 

 man, M.D., and Chas. H. White, M.D 546 



On some Points in the Phylogeny of the Tunicata. 



By Prof W. A. Herdman 546 



Scientific Serials . . 547 



Societies and Academies 549 



Books Received 552 



