May 7, 1891] 



NATURE 



23 



whose valuable contributions to the knowledge of the crystalline 

 rocks of this district are well known. That the Lizard serpentines 

 are altered peridotites may be regarded as settled, but doubts 

 have been expressed as to their relation to other associated 

 rocks, and as to the meaning of a streaky or banded structure 

 exhibited by certain varieties. The authors, after reexamination 

 of a large number of sections, feel no doubt of the accuracy of 

 their original view that the peridotite was intruded into the horn- 

 blende schists and banded " granulitic " rocks, after these had 

 assumed their present condition. In it they find no signs of any 

 marked pressure metamorphism, either prior or posterior to 

 serpentinization. They have failed to connect the streaky or 

 banded structure with any foliation or possible pressure-structure 

 in the schists, and they can only explam it as a kind of fluxion- 

 structure, viz. as due to an imperfect blending of two magmas of 

 slightly different chemical composition, anterior to the crystalliza- 

 tion of the mass. The Porthalla sections have been examined 

 with especial care, not only because the serpentine is nowhere 

 so conspicuously banded, but also because its intrusive character 

 has been denied, both it and the hornblende schists being ascribed 

 to the alteration of a series of sedimentary rocks of suitable com- 

 position. For this view the authors have failed to discover any 

 evidence, and consider it contrary to stratigraphical and petro- 

 graphical facts. In regard to the genesis of the crystalline 

 schists, which for purposes of reference were divided by Prof. 

 Bonney into a "granulitic," a "hornblendic," and a "mica- 

 ceous " group, the authors show that in parts of the first the 

 more acid rock breaks through the more basic, as if intrusive, 

 in others they appear to be perfectly interstratified, the one 

 passing backwards and forwards, though rapidly, into the other. 

 But between these extremes, intervals can be found where the 

 two rocks seem as if partially drawn out together. The authors 

 are agreed that certainly one, probably both, of these rocks are 

 igneous, that when the basic rock was solid enough to be rup- 

 tured, the acid magma broke into it, and sometimes softened it 

 sufficiently to allow of the two flowing for some little distance 

 together, after which crystallization took place. In regard to 

 the hornblende schists, the authors are not yet satisfied that 

 either fluxion or mechanical crushing will account for every 

 structure which they have examined, and prefer to leave the 

 question, in certain cases, an open one. The most distinctive 

 features of the micaceous group appear due to subsequent earth- 

 movements, so that, though it exhibits some special character- 

 istics, the authors are doubtful whether it is any longer worth 

 while separating it from the hornblende schists. Of the igneous 

 rocks newer than the serpentine, the gabbro has received the 

 closest attention. It exhibits in places (especially in the great 

 dyke-like mass at Carrick Luz) a very remarkable foliation or 

 even mineral banding, which has been claimed as a result of 

 dynamo-metamorphism. The authors bring forward a number 

 of instances to establish the following conclusions : — {a) That 

 this foliation occurs most markedly where the adjacent serpentine 

 does not show the slightest sign of mechanical disturbance ; 

 {b) that it must be a structure anterior to the consolidation of the 

 rock ; (c) that it sets in and out in a very irregular manner ; 

 ((/) that when it was produced the rock was probably not a perfect 

 fluid. Hence they explain it also as a kind of fluxion structure, 

 produced by differential movements in a mass which consisted 

 of crystals of felspar and pyroxene, floating thickly in a more or 

 less viscous magma. The authors' investigations tend to prove 

 that {a) structures curiously simulative of stratification may be 

 produced in fairly coarsely crystalline rocks by fluxioned move- 

 ments anterior to crystallization ; and that {b) structures which of 

 late years have been claimed as the result of dynamo-meta- 

 morphism subsequent to consolidation must have, in many cases, 

 a like explanation. This is probably the true explanation of a 

 large number of banded gneisses which show no signs of crush- 

 ing and holocrystalline, but in their more minute structures 

 differ from normal igneous rocks. The authors have seen 

 nothing which has been favourable to the idea that pressure has 

 raised the temperature of solid rocks sufficiently to soften them. 

 A discussion followed, in which Mr. Teall, the Rev. E. Hill, 

 Prof. Hull, the President, General McMahon, and Prof. Bonney 

 took part. — On a spherulitic and perlilic obsidian from Pilas, 

 Jalisco, Mexico, by Frank Rutley. 



Royal Microscopical Society, April 15.— Dr. R. Braith- 

 waite. President, in the chair. — Mr. T. Charters White presented 

 three slides of sections of teeth permeated with collodion. — A 

 letter from Mr. J. Aitkin, of Falkirk, was read, on a spot-mirror 



NO. 1 1 23, VOL. 44] 



method of illumination. — An abstract was read of a paper, by- 

 Surgeon V. Gunson Thorpe, R.N., on some new and foreigD 

 Rotifera found on the West Coast of Africa, and belonging to 

 the genera Trochosphara and Floscularia. — Mr. E. M. Nel- 

 son exhibited two forms of bull's-eye condenser— one made like 

 Herschel's asplanatic, the other a new and simpler form, being 

 made of two plano-convex lenses. This condenser seemed to 

 answer its purpose admirably, the amount of spherical aberration 

 being only about one-fifth of that which existed in the old form. 

 — Mr. Nelson also read some further notes on Diatom struc- 

 tures as test-objects, which he illustrated by photographs. — 

 Mr. C. Haughton Gill's additional note on the treatment of 

 Diatoms was read, the subject being illustrated by photo-micro- 

 graphs. Mr. Mayall said the problem Mr. GUI had endea- 

 voured to solve was as to the existence or not of cellular structure 

 in Diatoms extending through their substance, and he sought 

 to demonstrate this by making chemical depositions which would 

 probably fill up the cavities sufficiently to be distinguished by 

 the microscope. Mr. Gill's observations were of great interest, 

 because he had experimented with the definite purpose of testing 

 a special point, thus applying to microscopy \vhat Herschel 

 would have termed an "experiment of inquiry" — a direct 

 questioning of Nature on a point that had hitherto beea 

 regarded as almost beyond the sphere of experiment, 



Paris. 

 Academy of Sciences, April 27.— M, Duchartre in the 

 chair. — The Secretary read an extract from the will of the late 

 M. Cahours, and M. Janssen made some rem.arks upon the 

 legacies left for the foundation of scholarships (seep. 17). — On 

 the expressions of the pressures in an elastic homogeneous body, 

 by M. H. Resal.— On the theory of elasticity, by M. H. Poin- 

 care.— Researches upon humic substances, by MM. Berlhelot 

 and G. Andre. According to the observations of the authors, 

 the humic substance formed by the action of hydrochloric acid 

 upon cane sugar possesses etheric and anhydric properties, and 

 is comparable in certain respects to the lactones.— On the origin 

 of pus cells and on the rule of these elements in inflamed 

 tissues, by M. L. Ranvier. — On the performance of marine 

 engines and that of screws, and on a geometrical method for 

 calculating the first of these values without a dynamometer, ly 

 M. A. Ledieu. — Mica as an invariable dielectric, by M. E. 

 Bouty. The author has previously shown that the capacities of 

 mica condensers vary slightly with the duration of charging. He 

 now finds that mica behaves as an invariable dielectric in a direc- 

 tion normal to the planes of cleavage — that is, the capacity {c) of a 

 lamina of useful surface (p) and thickness {e) is represented by the 



formula c — ^ , where k is a constant. It is remarked that the 



origin of the large variations of such condensers with duration of 

 charging is the electrolysis of foreign substances contained in 

 the superficial layers— On an alternate current motor, by MM. 

 Maurice Hulin and Maurice Leblanc. — Quantitative studies on 

 the chemical action of light : first part — measure of physical 

 absorption, by M. G. Lemoine. The action of light upon 

 a mixture of oxalic acid and ferric chloride of various thicknesses 

 and strengths is theoretically and experimentally determined. — 

 Effisct of the presence of halides of potassium upon the solu- 

 bility of the neutral sulphate of potassium, by M. Ch. Blarez. 

 Between 0° and 30° the solubility of K2SO4 in water is given i& 

 parts per lOO by 



Qe = 8-5 -f- o 120. 



On adding KCl, or other halide of potassium, at any definite 

 temperature, the KgSOj remaining in solution is given by the 

 expression — 



K2SO4 dissolved = a constant - the amount of K in added salt ^ 

 for any temperature this becomes 



K2SO4 dissolved at 0° = 7-5 -f 0-14170 - K of added salt. 

 The precipitating action of the halides of potassium upon 

 the saturated solution of the neutral sulphate of potassium is 

 proportional to the equivalent of the added salt, — On iso-cin- 

 chonine, by MM. E. Jungfleisch and E. Leger. — On a hydro- 

 carbon of the terp,ene series contained in the oils of compressed 

 gas, by MM, A, Etard and P. Lambert. This is a pyropenty- 

 lene not identical with val>lene or pirylene ; it polymerizes 

 readily to Ci„H,2. Its properties and relations with the ter 

 penes will be given in a subsequent paper. — Researches upon 

 trehalose, by M. Maquenne. Anhydrous trehalose is an oct- 



