;6o 



NA TURE 



[February ii, 1S92 



by a discussion, in which Major-General McMahon, Prof. Judd, 

 Mr. Hudleston, Mr. Barrow, the Rev. Edwin Hill, and Prof. 

 Bonnev took part. — On the plutonic rocks of Garabal Hill and 

 Meall'Breac, by J. R. Dakyns and J. J. H. Teall, F.R.S. 

 (Communicated by permission of the Director-General of the 

 Geological Survey.) The plutonic rocks described occur in a 

 complex forming a belt of high ground south-west of Inverarnan. 

 'Ihey vary considerably in composition, and though gradual 

 passages are sometimes found between more or less acid rocks, 

 at other times the junction is sharp. The more acid are always 

 found to cut through the less acid when the two rocks are found 

 in juxtaposition, and fragments occurring in a rock are less acid 

 than the rock itself. Though thus shown to be of different ages, 

 they must evidently be referred to one geological period. The 

 first rocks to be formed were peridotites ; then followed diorite, 

 tonalite, granite, and eurite in order of increasing acidity. The 

 specific gravities, colours, and textures of the rocks are con- 

 sidered, and a detailed account of the constituent minerals given. 

 The essential minerals are arranged in the following order, based 

 on their general distribution in the different types of rock : 

 olivine, pyroxene, hornblende, biotite, plagioclase, orthoclase 

 and quartz, microcline. The following is the order in which 

 the principal constituents commenced to form in the rocks : 

 iron-ores, olivine, pyroxene, hornblende, biotite, plagioclase, 

 orthoclase, microcline, and quartz. The chemical composition 

 of the rocks is discussed, data being furnished by a series of 

 analyses made by Mr. J. H. Player, and a diagrammatic repre- 

 sentation of the molecular relations of the different bases and 

 silica is given. The relations between mineralogical composition, 

 chemical composition, and geological age are then considered ; 

 and the following conclusions are reached :-^( i ) That the various 

 rocks have resulted from the differentiation of an originally 

 homogeneous magma. (2) That the chronological sequence 

 from peridotite to eurite is connected with the order of formation 

 of minerals in igneous magmas. The paper was discussed by 

 Dr. Hatch, Prof. Bonney, and Mr. Barrow. — North Italian 

 Bryozoa ; Part II. Cyclostomata, by Arthur Wm. Waters. 



Paris, 

 Academy of Sciences, February i.— M. D'Abbadie in the 

 chair. — Note on a structure placed on the summit of Mont 

 Blanc, by M. J. Janssen. It will be remembered that, after 

 failing to reach the rock through the snow on the top of Mont 

 Blanc, M. Janssen, last October, made some observations in a 

 temporary hut for the purpose of testing whether it was displaced 

 appreciably by the movement of the snow. The observations 

 failed to indicate any movement. On January 2 the hut was 

 visited by M. Dunod, and some observations made in it at M. 

 Janssen's request show that no change of place has occurred 

 during this interval of four months. — Observations of solar spots 

 and faculse made with the Brunner equatorial (o"i6 metre aper- 

 ture) of Lyon Observatory during the latter half of 1891, by M. 

 Em. Marchand. (See Our Astronomical Column.) — Temperate 

 regions ; local conditions of persistency of atmospheric currents ; 

 derived currents ; origin and translation of certain cyclonic 

 movements, by M. Marcel Brillouin. — On an extension of 

 Sturm's theorem, by M. E. Phragmen. — On Laplace and La- 

 voisier's apparatus for measuring the linear expansion of solids, 

 by M. E. Grimaux. The author has come into the possession of 

 some copper-plates drawn by Lavoisier in illustration of his 

 method of determining the coefficient of linear expansion. Pulls 

 have been obtained from these plates and presented to the 

 Academy. — On the compressibility of saline solutions, by M. 

 Henri Gilbault. — On electro-capillary phenomena, by M. Gouy. 

 — On the optical determination of high temperatures, byM. H. Le 

 Chatelier. Some experiments have been made with the idea of 

 measuring high temperatures by determining the intensity of the 

 radiations emitted by a pyrometer of platinum, or clay, or other 

 material, when compared with the light of a standard lamp. The 

 results obtained indicate that the method is a good one. The 

 principal difficulties, of course, depend upon the fact that the radia- 

 tions emitted by an incandescent body are affected by conditions 

 other than temperature. M. Le Chatelier, however, seems to 

 have satisfactorily overcome these difficulties. — On achromatism, 

 by M. A. Broca. — Barium and strontium nitrides, by M. 

 Maquenne. These nitrides are formed by the direct action of 

 nitrogen at a red heat upon the metals obtained from amalgams 

 formed by electrolysis. The analyses given prove their composi- 

 tion to be represented by NjBag and NgS^s respectively. They 

 yield ammonia on treatment with water, and may be viewed as 



NO. I 163, VOL. 45] 



metallic ammonias. Barium nitride does not give ethyl bases 

 when treated with alcohol. It reacts energetically at a red heat 

 with carbon monoxide, producing barium cyanide and oxide. 

 Strontium nitride similarly yields only a trace of strontium 

 cyanide, the chief products being the oxide, carbonate, 

 and carbon. — Carbon chlorobromides, by M. A. Besson. 

 (See Notes.)— Action of metals on salts dissolved in or- 

 ganic liquids, by M. Raoul Varet. Certain metals, able to 

 precipitate others from their salts dissolved in water, lose this 

 property when certain organic liquids are used as solvents. 

 This difference of action is due somewhat to the water and 

 somewhat to the formation of molecular compounds formed by 

 the union of the products present. — On monosodium mannite, 

 by M. de Forcrand. — Transformation of sulphanilic into sulph- 

 anilocarbamic acid in the animal economy, by M. J. Ville. — 

 Chemical study of the chlorophyll bodies of the pericarp of the 

 grape, by M. A. Etard. — Researches on the adherence to the 

 leaves of plants, and notably to the leaves of the potato, of 

 copper compounds used to prevent their diseases, by M. Aime 

 Girard. — Development of the organe -vibraiile of Composite 

 Ascidise, by M. A. Pizon. — On the locust {Schistocerca pere- 

 grina, Oliv.) and its changes of colour ; rSle of the pigments in 

 the phenomena of histolysis and histogenesis which accompany 

 the metamorphosis, by M. Kunckel d'Herculais. — On the com- 

 mencement and extinction of cambial activity in trees, by M. 

 Emile Mer. — Absolute surfaces and relative divisions of the 

 earth occupied by the principal geological groups, by General 

 Alexis de Tillo. The author states the relative surfaces, of 

 each of the present continents, which existed in different geo- 

 logical periods. — Investigation of the nature of the waters and 

 mud of Lake Annecy, by M. L. Duparc. 



CONTENTS. PAGE 



The Vacant Chair of Astronomy at Cambridge. . . 337 



The Catalogue of Scientific Papers. By X 338 



The Aneroid in Hypsometry. By H. F. B 339 



Waller's Human Physiology. By Dr. E. H. Starling 340 

 Our Book Shelf:— 



"Bulletin of the New York Mathematical Society". 341 



Harrison : " Guide to the Examinations in Chemistry " 342 



Bausch : " Manipulation of the Microscope" .... 342 



Barrett-Hamilton: *' Harrow Birds " 342 



Letters to the Editor:— 



The Theory of Solutions.— J. W. Rodger .• ... 342 



Arrow Poison. — A. Coppen Jones 343 



The Implications of Science. — Dr. St. George 



Mivart, F.R.S 343 



The New Forest in Danger. — Herbert Goss . . . 343 



On the New Star in Auriga 344 



Mr. Tesla's Lectures on Alternate Currents of High 



Potential and Frequency. By A. W. R. ; G. , . 345 



Wave-Motion Model. {Illustrated.) By F. Cheshire 347 

 The Science Museum and Gallery of British Art at 



South Kensington 348 



Notes 348 



Our Astronomical Column :— 



Report of the U.S. Naval Observatory 352 



Observations of Nebulae and Star-Clusters 352 



Solar Observations 352 



Measures of the Nebula near Merope 352 



Journeys in the Pamirs and Adjacent Countries. By 



Captain F. E. Younghusband 353 



The Institution of Mechanical Engineers 355 



The Electrical Exhibition 356 



University and Educational Intelligence 356 



Scientific Serials 357 



Societies and Academies 357 



