Jan, 25, 1877] 



NATURE 



285 



port the overlying weight. Communication is dependent upon 

 the use of snow-shoes. 



The Prussian Universities granted during the past year 500 

 doctor's diplomas upon the basis of a thesis and oral examina- 

 tion. Gottingen bestowed 139, Berlin, 90. Twenty honorary 

 degrees were granted during the same period. 



M. Fjzeau has been elected Vice-President of the French 

 Academy of Sciences for the coming year, from the section of 

 the mathematical sciences j the President is M. Peligot. Of 

 the Academy's Meutoires, tome xxxix., in course of publication, 

 is reserved for works of M. Chevreul, on dyeing, on an error 

 of reasoning frequent in sciences which are concerned with the 

 concrete, science in relation to grammar, history of opinions 

 on the chemical nature of bodies of chemical and living species, 

 &c. The Academy is also publishing a number of documents 

 on the Transit of Venus. Tomes xxiii., xxiv., and xxv. of 

 Memoires des Savants Etrangers contain memoirs on the theory 

 of running waters, a system of irrigation, the succinic series, the 

 carboniferous flora of the department of the Loire, the trans- 

 formation and equivalence of chemical forces, the transparence 

 of flames, vision of scintillating lights and nocturnal transparence 

 of the atmosphere, the Phylloxera, &c. 



The Bulletin de la Federation des Societes d'' Hortiadture de 

 Belgique for 1875 is just published, and illustrates the great 

 activity with which this branch of science is pursued in the little 

 kingdom. Besides the official papers connected with the federa- 

 tion, and reports from twenty-five associated societies, the volume 

 contains the " Correspondance botanique" for that year, a list 

 of botanists and horticulturists holding ollicial positions through- 

 out the world, a sketch of the life of Mathias de I'Obel (Lo- 

 belius), by E. Morren, and several other papers by the same 

 writer. 



Mr. Thomas Comber reprints from the Transactions of the 

 Historic Society of Lancashire and Cheshire, a useful paper en- 

 titled '* Geographical Statistics of the Extra- British European 

 Flora, " containing a considerable mass of information which 

 will be valuable to anyone interested in the subject of the dis- 

 tribution of continental species, and the causes of the range 

 which they now enjoy. 



Hungary is developing no small degree of activity in matters 

 of scientific interest. The pi-esident of the Royal Society for 

 Natural Sciences at Pesth reported in the annual Session of 

 January 17, that the present membership amounts to 4,650. 

 Five subjects for prize treatises were announced, one of which 

 was on the chemical resources and industries of the kingdom. 



The phenomenon of the "black drop " has recently been made 

 the subject of experimental study by M. Ch. Andre, who ha« 

 communicated his results to the French Academy. Without 

 stopping to describe his artificial transit, we may state that he 

 had a battery communicating with the planet Venus, the other 

 with the limb of the sun ; and at the moment of geometrical 

 contact a current was produced, which was registered on a 

 Brequet chronograph. On the same instrument was inscribed 

 parallelly the hour given by a Winnerl pendulum, and the mark 

 produced by the observer pressing down a Morse key. The con- 

 clusions of M. Andre are, shortly, as follows : The black drop is 

 not an accidental fact, but one that is necessary and character- 

 istic of the phenomenon. "With sufficiently strong light, the 

 bridge is always produced at the moment of geometric con- 

 tact, however perfect the telescope. It may be made to dis- 

 appear entirely in the retinal image, either by increasing suffi- 

 ciently the absorbent power of the dark glass used, or by placing 

 before the objective a screen formed of a large number of very 

 narrow rings separated by dark rings of the same width, also by 

 diminishing the intensity of the luminous^source. In each case 



the transit is produced in a geometric manner. All these facts 

 accord with the theory of diffraction rightly interpreted. The 

 ligament is not a real obstacle to observation of the transit. 

 There is a simultaneous p/use iot all telescopes, whatever their 

 apertures, which corresponds to geometric contact, and after a 

 suitable education one may observe with an error equal at the 

 most to o'75s. for internal contact of ingress, and i'5os. for in- 

 ternal contact of egress. The total error, then, may be re- 

 duced to 2 '58. Now to have the solar parallax to a hundredth 

 of second of arc, it is sufficient not to commit, in the duration 

 of transit, an error above five seconds of time ; hence the 

 observation of the transit of Venus may furnish this parallax to 

 nearly five-thousandths of a second of arc. 



A PAIR of Kcenig Ut* forks will show the phenomenon ot 

 sympathetic resonance at much greater distance than a pair of 

 Ut^ forks. The common explanation is that as double the 

 number of impulses are delivered in a second, double the energy 

 is conveyed to the distant fork. This is questioned by Mr 

 Robert Spice {American Journal of Science and Arts), in view 

 of the law of forces radiating from a centre. At twenty feet, in 

 fact, the intensity of resonance of Ut* forks is undoubtedly 

 greater than the intensity of Ut^ forks at six feet. With Ut' 

 forks of bell-metal he got, at forty feet, a greater result than that 

 obtained with the steel Ut* forks of Koenig. The hypothesis he 

 offers is this : The intensity of sympathetic resonance of forks on 

 their cases increases with the angular deviation or motion of the 

 prongs. By means of an electro-chemical registering apparatus 

 Mr. Spice finds that when a fork (between Ut* and Ut*) is in 

 vibration, its stem or handle alternately rises and falls in accord 

 with the period of the fork, through about -^^ inch. In sympa- 

 thetic resonance the case gives the stem this up-and-down motion, 

 which is conveyed to the prongs and sets them in motion, as a 

 hand might start a pendulum suspended from it (by moving late- 

 rally, say, one inch each way). This motion of ^V i"ch may be 

 looked on as a constant If we decrease the length of the fork 

 without altering the constant, we thereby allow of a greater 

 initial angle, the result of which is the same as shortening the 

 pendulum cord. Thus we are in a position to explain the deport- 

 ment of the bell-metal forks. The velocity of sound in bell- 

 metal is much less than in steel ; hence, retaining similar thick- 

 nesses in both cases, an Ut^ fork in bell-metal would be shorter 

 than an Ut^ fork in steel. Therefore, though we retain the 

 vibration number, we gain advantage from , the shortness 01 

 the fork, and hence from the increase of angular motion of 

 the prongs. 



The applicability to liquids of Kirchoff's law as to the sub- 

 division of galvanic currents in bifurcating metallic conductors 

 having been doubted. Prof. Lenz has recently {Bull, de I' Ac. 

 de St. Petersh., vol. xxii.. No. 3) made a series of experi- 

 ments with solutions of sulphates of copper and zinc and of 

 nitrate of silver. He arrives at the conclusion that the sub- 

 division of galvanic currents in liquids follows exactly the same 

 laws as their subdivision in metallic conductors. 



In a paper "On Evolution in Geology," in the January 

 number of the Geological Magazine, Mr. W. J. Sollas, starting 

 from the ground that the energy of the earth and the sun is a 

 continually diminishing quantity, and must at the beginning of 

 geological history have been far in excess of its present amount, 

 briefly discusses the influence of this greater quantity of energy 

 on geological changes. He arrives at the conclusion that all 

 main factors of geological changes, viz., the denudation, repro- 

 duction, and the elevation and depression of strata, must have 

 notably and rapidly decreased in intensity ; and, alluding to the 

 opposition met with from geologists by Sir W. Thomson's views, 

 he insists on the mistake of attempting to check^the results as to 

 the age of the world obtained by the physicist with those de- 



