March 29, 1888] 



NATURE 



527 



fluence of these electricities, that electricities. of different kinds 

 attract each other, and those of the same kind repel each other. 

 De Saussure's and Volta's electroscopes were next described, 

 pith-balls being used in the former and blades of straw in the 

 latter for testing the pressure of electricity. With the object of 

 measuring the force of electricity, Sir W. Thomson's electro- 

 meter was mentioned, in which the electricity is collected from 

 the air by means of an insulated cistern letting out water drop 

 by drop, each drop becoming covered with electricity from the 

 atmosphere, which runs into the cistern where it is stored up, 

 and made to act upon that portion of the instrument which 

 records its degree or amount. The atmosphere is always more 

 or less electrical, or, in other words, possessed of electrical ten- 

 sion, and this is nearly always positive ; while the earth 

 exhibits electrical characters of a negative kind. The effects of 

 atmospheric electricity were classed by Dr. Marcet under three 

 heads : (i) lightning in thunderstorms; (2) the formation of 

 hail ; (3) the formation of the aurora borealis and australis. 

 He explained how clouds acquired their electrical activity by 

 remarking that clouds forming in a blue sky, by a local conden- 

 sation of moisture, became charged with positive electricity from 

 the atmosphere ; while heavy dark clouds rising from below 

 nearer to the earth were filled with terrestrial negative electricity, 

 and the two systems of clouds attracting each other would dis- 

 charge their electricity, giving rise to flashes of lightning. In 

 some cases a storm-cloud charged with positive electricity would 

 approach the earth, attracting the terrestrial negative electricity, 

 and when within a certain distance shoot out lightning which 

 would apparently strike the earth ; but it would just as well 

 have struck the c'oud, only there was nothing in the cloud to 

 sustain any damage, while on the earth there were many objects 

 lightning would destroy, to] say nothing of its effects upon 

 animal life. Thunder is the noise produced by the air rushing 

 in to fill up the vacuum made by the heat of the lightning flash. 

 There may be sheet lightning, zig-zag or forked lightning, or 

 globular lightning. The latter is particularly interesting from 

 its assuming a spherical form. Illustrations were given of 

 objects struck by lightning, the most remarkable being, perhaps, 

 the clothes of a working man which were torn into shreds, while the 

 man himself was not seriously injured. Dr. Marcet next proceeded 

 t;oshow a flash of lightning, which he produced by throwing on 

 a white screen the ima^e of an electric spark 2 or 3 inches in 

 length, enlarged by means of the lens of an optical lantern ; 

 forked lightning, 6 or 8 feet in length, with its irregular zig-zag 

 I course, was most clearly demonstraterl. After alluding to the 

 I protecting power of lightning conductors and their construction, 

 Dr. Marcet explained the formation of hail and waterspouts, 

 and exhibited an instrument by Prof Colladon, of Geneva, for 

 showing the formation of waterspouts. He concluded his ad- 

 dress witha few remarks on the aurora borealis and australis, 

 the formation of which was illustrated by de la Rive's experi- 

 ment, which consisted of successive discharges of electric sparks 

 through a partial vacuum while under the influence of a power- 

 ful magnet ; electric sheets of light were seen assuming the form 

 of bands and possessed of a certain rotating motion. — Mr. G. J. 

 Symons, F.R. S., read a short commuication on the non-existence 

 of thunderbolts, and briefly described the history of several so- 

 called thunderbolts, the specimens obtained being of an amusing 

 character, thus clearly showing that they were of a terrestrial 

 and not a celestial character. 



Edinburgh. 



Royal Society, February 20. — Sir W. Thomson, President, 

 in the chair. — A preliminary note on the duration of impact, by 

 Prof. Tait, was communicated. The results already obtained 

 were got by means of a roughly made apparatus designed for 

 the purpose of testing the method used. When a wooden bloc'c 

 of 10 lbs. mass fell through a height of 18^ inches on a rounded 

 lump of gutta-percha, the time of impact was found to be o"ooi 

 sec, and the coefficient of restitution was o"26. — A paper on a 

 bathymetrical survey of the chief Perthshire lochs was read by 

 Mr. J. S. Grant Wilson of H.M. Geological Survey. Lochs 

 Rannoch, Tummel, Earn, and Tay, were specially dealt with. 

 In the discussion which followed, Sir W. Thomson remarked 

 that he did not consider that the ice had much to do with the 

 formation of rock basins. Where it found a rock basin already 

 in existence it might increase its dimensions, — Mr. H. M. 

 Cadell, H.M, Geological Survey for Scotland, read a paper, of 

 which an abstract appeared in our last issue (p. 488), on experi- 



mental researches in mountain building. — Mr. Peach communi- 

 cated a paper by Dr. Ernst Stecher on contact phenomena of 

 some Scottish olivine diabases. 



March 5. — Mr. J. Murray, Vice-President, in the chair. — Mr. 

 W. E. Hoyle communicated a paper by Mr. D. McAlpine on 

 observations on the movements of the entire detached animal, 

 and of detached ciliated parts of bivalve mollusks, viz. gills, 

 mantle-lobes,labial palps, and foot. — TheChairman communicated 

 a report on the fishes which he had obtained in deep water on 

 the north-west coast of Scotland. The report was drawn up by 

 Dr. A. Giinther, F. R.S., Keeper of the Zoological Department, 

 British Museum. — Prof. Haycraft read a paper by Dr. Carlier 

 and himself on the morphological changes which take place in 

 blood during coagulation. — A paper by Prof. Tait on the mean 

 free path, and the number of collisions per particle per second 

 in a group of equal spheres, was communicated. In this paper 

 Prof, Tait cited De Morgan's definition of the term "mean," 

 and pointed out the difference between the mean free path, 

 properly so called, and the quantity to which that name is usually 

 applied. — A preliminary note by the same author on the com- 

 pressibility of glass at different temperatures was also read. The 

 glass experimented upon was ordinary lead glass. At 8° C. the 

 compressibility per atmosphere is 0^0000027, and increases by 

 o'ooooooo2 per degree Centigrade of rise of temperature, 



March 19. — Sir W. Thomson, President, in the chair. — 

 Mr. George Seton read a paper on illegitimacy in the parish 

 of Marnoch. — Dr. G. Sims Woodhead communicated some 

 notes on the use of the mercuric salts as antiseptic surgical 

 lotions. — In a paper on the effect of diff'erential mass-motion on 

 the permeability of gas. Prof Tait gave the calculations which he 

 promised in his reply to Prof Boltzman published in the Philo- 

 sophical Magazine. — The President read the second part of a 

 paper by Mr. J. J. Coleman, on a new diffusimeter, and other 

 apparatus for liquid diffusion, and discussed the determination of 

 diffusivity in absolute m3asure from Mr. Coleman's experiments. 

 — Sir W. Thomson also read an extract from a letter of the 

 late William Froude to himself, dealing with the soaring of 

 birds. Mr. Froude showed that in all cases soaring is de- 

 pendent on the existence of upward air currents. In the case of 

 a complete calm at sea, the upward current is produced by dis- 

 placement as a wave passes underneath. — Mr. W. Peddie read a 

 preliminary note on new determinations of the electric resistance 

 of liquids by a method based upon Joule's law, and which 

 therefore avoids any error which might be caused by transition- 

 resistance or polarization. — Mr. C. A. Stevenson gave a notice 

 of the recent earthquake in Scotland, with observations on those 

 since 1882. 



Paris. 



Academy of Sciences, March 19. — M. Janssen in the 

 chair. — On certain points connected with the theory of ac- 

 cidental errors, by M. Faye. It is argued that the arithmetical 

 mean does not necessarily and in all cases give the most prob- 

 able result. The law of error can be regarded only as a simple 

 approximation to the truth, although so far valuable that it may 

 be freely applied to all sorts of observations and measurements, 

 provided they be exempt from systematic error. The danger 

 lies in excluding all extremes which might have the effect of 

 enabling the observer to draw any conclusion he pleases, or 

 which squares best with some preconceived view. The same 

 subject is discussed in a paper by M. J. Bertrand on the prob- 

 able value of the smallest errors in a series of observations. — 

 On a point in the theory of the moon, by M. F. Tisserand. The 

 object of these remarks is to determine in Delaunay's theory of 

 the moon the full scope and application of the theorem of the 

 invariability of the great axis of the lunar orbit. The demon- 

 stration here induced from Delaunay's method is extremely 

 simple, and leads to some further interesting inductions, — New 

 theory of the equatorial coude, by MM, Loewy and P, Puiseux. 

 The paper deals with the corrective terms depending on the 

 inner glass and the axis of declination. In a future paper will 

 be given the terms depending on the outer glass, together with 

 the complete formulas of reduction. — On the absorption of saline 

 substances by plants, by MM. Berthelot and G. Andre, The 

 experiments here described are mainly confined to the sulphate 

 of potassa, and will in future be extended to other substances 

 with a view to elucidate the obscure processes by which plants 

 derive their mineral elements from the soil. The solution of the 



