NA TURE 



IDec. 20, 1883 



(iver those in the first, those in the eighth over those in the 

 second, and so on (Figs. 5 and 517). 



When we inquire whether the symmetrical arrangements just 

 traced are in harmony with the facts respecting compounds of 

 two l<inds of atoms in the proportions i : 2, we find some very 

 important evidence. 



Thus uater, H.>0, crystalhses in six-sided prisms or in rhombo- 

 hedra ; forms both of which are compatible with one or other 

 of the above symmetrical arrangements. 



And the following most interesting concurrence of facts indi- 

 cates that the symmeti ical arrangements in the fourth kind of 

 symmetry above described (see Figs. 5 and 5a) are tho^e of 

 the atoms of quartz. 



(n) Quartz consists of oxygen two atoms, silicon one atom ; 

 just the proportions in these arrangements. 



{b) it has the property of circular polarisation, from which it 

 has been proved that its molecules must have a spiral arrange- 

 ment, and, since some crystals have the property of rotating in 

 one direction, some in the opposite, that this spiral arrangement 

 is right-handed in some crystals, lelt-handed in others. 



(c) It crystalhses in six-sided prisms terminated by six-sided 

 pyramids, a form derivable, as we have seen, from the arrange- 

 ments before us. 



As to this last point, just a word of explanation why we must 

 not look for the angles exhitited by our model arrangements to 

 be identical with the angles made by the pyramid faces in quartz. 



It is a matter of common observation that the process of 

 crystallisation is generally associated with change of bulk, 

 and if v\e suppose this change to arise from expansion, 

 or contraction, generally expansion of the ditferent kinds of 

 atoms, and that these different kinds have difftrciit decrees 

 of expansion, we see that a mass symmetrically arranged 

 in the manner supposed will in crystallising expand or contiact 

 more in some directions Ihan in others, and while we should look 

 for a similar change in the direction of each of the three trans- 

 verse subordinate axes of the crystal, we should look for a 

 different change in the direction of the principal axis. And 

 thus, supposing the mass when liquid immediately before it 

 began to crystallise to have hid the internal symmetry which has 

 been depicted, it is evident that the unequal chan e of dimension 

 in different directions might suffice to bring about such an incli- 

 nation of the faces of the terminal pyramids to the sides of tbe 

 prism as is actually found to exist. 



In support of this explanation we have the fact that crystals 

 not of the regular system have been found to expand unequally 

 in different directions when subjected to heat. 



Farther evidence in support of the theories here submitted is 

 found in the fact that, with scarcely any exception, the com- 

 pounds we are now considering do not crystallise in the reguUr 

 or cubic system.' William Barlow 



( To be continued. ) 



THE HELVETIC SOCIETY OF NATURAL 

 SCIENCES 

 'VHE sixty-sixth session of this Society was held early in the 

 month of August of the present year in the city of Zurich. 

 The proceedings cf the various Mathematical, Physical, Chemi- 

 cal, Zoological, Botanical, and Medical Departments are some- 

 what fully reported in the Aic/iives des iiciences Physiques et 

 Niilurdles, Geneva, October 15. On August 6 a preliminary 

 meeting was held of the delegates of the Lantonal Sections and 

 Special Comu^ittees, and next day the session was formally 

 opened in the Town Hall under the presidency of Prof. Cramer. 

 The two ensuing days were devoted to the work of the several 

 Sections, all of which were well attended by numerous Swiss and 

 foreign savants, brought together by the double attraction of the 

 Helvetic Society ana the National Exhibition, which was also 

 held this year in Zurich. 



In the Mathematical Section, over which Prof. W. Fiedler pre- 

 sided, the chief papers were those of Prof. Geiser (Zurich), on 

 surfaces of the third degree; of Dr. Kudio (Zurich), on the 

 geodetic lines traced on surfaces of the second degree ; of Prof. 

 Fiedler (Zurich), on the inter ectiun of equilateral hypcrboloids 

 revolving on parallel axes. 



In the Physical Section, presided over by Prof. R. Clausius, 



^ With regard to calcic fluoride (fluor-spar), which appears as an exception, 

 it may be remarked that a different at.-niic weight for calcium which would 

 enable us to write the compound CaF would enable us to get over a difficuhy 

 with regard to another compound cf calcium, as we shall see presently. 



M. F. A. Forel (Morges) communicated the result of his re- 

 searches made todeiermine the limits of variation of temperature 

 in the waters of Lake Geneva. According to his thermometrical 

 soundings, the diurnal variatijn is perceptible down to a depth 

 of from 10 to 15 metres; the summer variation from 60 to 100 

 metres. Excepiional winters like that of iSyg-bo are felt as 

 low as 334 metres. Since that year the temperature of the 

 water at these great depths has been raised on an average about 

 half a degree Centigrade. 



Some preliminary results of his researches on the refraction 

 ai.d dispersion ot crystallised alums were communicated by M. 

 Charles Soret of Geneva. By means of his completely reflecting 

 refractonieter, described in the Archives for January, 1883, the 

 author has determined the indices of refraction for the principal 

 lines of the solar spectrum from a to G inclusively for six 

 sulphuric alums with alumina ba^e. 



Prof. Clausius read a paper of practical importance on the 

 theory and proper method of construction of dynamo-eleciric 

 machines. Some curious experiments were made by M. C. de 

 Candolle of Geneva, showing how ripples are formed on sandy 

 surfaces at the bottom of the sea. F rom these experiments it 

 re ult» that the phenomenon is produced by the friction of a 

 liquid mass against any substance more viscous than itself. 

 Hence the sand maybe regarded as forming with the water a 

 vi-cous mixture, on the surface of which the friction of the pure 

 liquia develops ripples in the same w ay that the friction of the 

 air develops rippiles on the surface of the water itself. 



Amongst the other memoirs in the Physical Section the most 

 noteworthy were thoac of Prof, H. F. \\ eber (Zurich) on liquids 

 and gase.s as heat coiiductors ; an experimental demonstration of 

 the second principle of the mechanical theory of heat, byM. 

 Kami Pictet ; on the determination of the ohm, by Prof. H. F". 

 Weber ; on the results ot the observations and researches made 

 in the laboratory of the Lausanne Academy on atmospheric 

 electricity, by M. Henri Dufour of Lausanne. The author de- 

 scribed several successful attempts made by him to reproduce 

 artificially the cleciiic piherromena observed in the terrestrial 

 atmosphere. 



The Chemical Section was opened, under the presidency of 

 Prof. Wisliccnus, by Prof. V. Meyer's memoir on the nature 

 ol the chemical elements according to recent research. The 

 author leans to the vievis of Mendeleeft and Lothar Meyer, who 

 regard the properties of simple bodies as the periodical functions 

 of their atomic weights. The fact that MendeleeH was able to 

 predict the existence of gahium and scandium, and correctly 

 determine their atomic weights, was adduced in support of the 

 theory that all the elements are merely different compound forms 

 ot one primidve sub^tance. Hence, although hitherto baftled, 

 the attempts now being made to decompose them may result in 

 the experimental determination of one absolute primordial 

 substance. 



Prof. F. Krafft (Basle) presented some higher alcohols of the 

 series C„H„„ + 20, acciimpanying them with some remarks on 

 the synthesis of alcohols in general. A resiimi was given by 

 Prof. Louis Soret (Geneva) 01 hi^ researches on the absorption 

 cf the ultra-violet rays by various substances of animal origin. 

 The author dwelt on the great importance of thl^ branch of 

 spectral analysis to chcnii-try, and concluded with a brief 

 description ot the method and appliances used by him in his 

 original re.-earchcs. 



(Jther valuable chemical papers were those of Dr. M. 

 Ceresole (Lausanne), on acetacetic acids; of Prot. V. Me)er on 

 the apparatus used in determining the densities of gases at very 

 high temperatures ; of Prof. Schulze, describing the researches 

 made by tiim jointly with M. J. Barbieri on phenylamidopro- 

 pionic acid, which is obtained by heating albuminoid substances 

 with chlorhydric acid ana chloride of tin ; of Prol. Wislicenus 

 (Wurtzburg), on the relation of the optical rotatory power of 

 carburets ol hydrogen, on the existence of an atoui of asymmetric 

 carbon, and on the products of the reaction of dichloride of 

 phtalyle on the sodic combination of maloiiic ether ; Prof. G. 

 Lunge (Zurich), on the formation of sulphuric acid in lead 

 chambers; Dr. lirech (^Stuttgart), on a lamp fed by ether of 

 petroleum. This lamp, constructed by C. C. Lilienfein, of 

 Stuttgart, consists of a metallic receiver containing the ether of 

 petroleum, and connected with a liunsen burner slightly modified 

 in consequence of the liquid nature of the combustible. 



In the Zoological Section Prof. C. Vogt, president, the pro- 

 ceedings were opened by a communication from Prof. il. Fol 

 (Geneva), on the physiological origin of the individual in the 



