Nov. 1 8, 1886] 



NA TURE 



67 



is impossible to place much confidence in arguments based upon 

 llie study of such complex phenomena. 



As regards the question of chemical versus mechanical action, 

 the speaker could only imagine one form of mechanical action 

 attending dissolution, viz. that of the water molecules bombard- 

 ing the surfaces of the solid, and as it were chipping off particles. 

 All other actions, in so far as they could be regarded as involving 

 the attraction of the molecules of the dissolved substance by 

 those of the solvent, he was inclined to class as chemical. No- 

 thing was more certain than that dissolution depended on the 

 nature both of the solvent and of the su' stance dissolved. Like 

 dissolves like — water K//ie solvent for bodies containing oxygen ; 

 sulphur compounds are dissolved by carbon bisulphide ; phos- 

 phorus coinpounds by chloride of phosphorus ; shale spirit, 

 which is rich in olefines, and especially rosin spirit, which is rich 

 in acetylenes and benzenes, were far better solvents of hydro- 

 carbons and resinous bodies than petroleum, which consisted of 

 saturated inert hydrocarbons, and was the worst of solvents. 

 Facts such as these spoke strongly in favour of the conclusion 

 that the phenomena of dissolution are largely of a chemical 

 character. 



Prof W. N. Hartley was understood to base the argument in 

 favour of the hydration theory chiefly on the changes of colour 

 observed in the solution of certain salts in various proportions of 

 water. The chlorides, bromides, and iodides of cobalt, nickel, 

 and copper exhibit these phenomena most plainly. Thus the 

 iodide of cobalt in the anhydrous s ate is black, its dihydrate is 

 green, the hexhydrate a reddish brown. If this last be dissolved 

 in water a ]5ink solulion is formed, which probably contains a 

 richer hydrate. The brown saturated solution of the hexhydrate 

 is a very dense liquid, of specific gravity about 3, and when 

 water is added to it the formation of the pink liquid is attended 

 by a large evolution of heat, and this afl'ords evidence that the 

 hydrate exists in the solution. Again, hydrated cupric chloride 

 contains two molecules of water, and when quite dry is of a pale 

 blue colour. Its solution in water has the same colour unless it 

 l>e heated, and then it turns green. Nickel salts behave simi- 

 larly. .So that the evidence, on the whole, warrants the belief 

 that when a hydrated salt is dissolved in water the water of 

 crystallisation remains a constituent part of the molecule. 



Dr. Gladstone commenced his remarks by a discussion of the 

 question, What is a salt in solution ? Is the solution of a salt in 

 water a process analogous in any degree to the decomposition 

 which takes pl.ace when one salt is mixed with another ? Take, 

 for instance, chloride of sodium and water. Many years ago the 

 speaker had endeavoured to determine whether any chemical de- 

 composition of the salt by the water occurred so as to give rise 

 to sodium hydrate and hydrochloric acid, but he had come 

 to the conclusion that this decomposition took place, if at all, 

 only to a very small extent. Many salts, as had already been 

 stated, combine with water to form coloured hydrates, and the 

 hydrate is of a colour diflTerent from that of anhydrous salt. 

 Kut a coloured hydrate, when dissolved in a sufficient quantity 

 of water, is never changed by further dilution. The speaker had 

 endeavoured to ascertain whether the specific refraction of sub- 

 stances was altered by solution. lie had found that no alter- 

 ation could be detected, and this result was afterwards confirmed 

 by the experiments of other chemists. The refraction equivalent 

 of a solution is equal to the sum of the refraction equivalents of 

 the salt and the water present. In an alum solution, the water 

 of crystallisation supposed to be in combination with the salt is 

 not distinguishable by its refractive power from the water of 

 solution outside it. It seems impossible, however, to arrive at a 

 conclusion w-ith regard to the constituents of a solution. The 

 idea of reciprocal decomposition is not supported by experi- 

 mental evidence, save in some exceptional cases, and the actual 

 condition of a dissolved salt seems beyond expression by 

 fonnulse. 



TEN YEARS'- PROGRESS IN ASTRONOMY 

 "pHE Emi/i. — In what may be called the astronomy of the 

 earth there is no very great discovery, nothing extremely 

 new .and brilliant to record during the past decide ; but there 

 has been considerable and steady progress. 



(a) As regards the earth's form and dimensions, it has become 

 quite certain that Bessel's ellipticity (1/300) is too small. 

 Clarke's value of 1/294 i^ now admitted and employed on the 



' "Ten Years' Progress in Astronomy, 1876-36, " by Prof. C. A. Young. 

 Read May 17, 1S86, before the New York Academy of .Sciences. 



U.S. Coast Survey with a decided improvement of accordance. 

 A slightly larger value even is suggested by the most recent 

 pendulum observations, and 1/292 is now adopted in Europe. 



One of the most important steps in this branch of investigation 

 is the discovery by Mr. Peirce (of our own Coast Survey), of the 

 large correction required in many former pendulum determina- 

 tions, on account of the yielding of the stand fj'om which the 

 pendulum is suspended. 



During the past ten or fifteen years a great amount of material 

 has been collected towards a complete gravitational survey of 

 the earth, by the work of Lieut. -Col. Herschel in India, and of 

 the officers of the Coast Survey in this country and elsewhere, 

 and a very important part of it has consisted in connecting the 

 older work with the new, by Peirce's operations in Europe, and 

 those of Herschel in this country. 



At tlie same time it has become incieasingly evident that very 

 little is now to be gained by endeavouring to find a spheroid 

 fitting the earth's actual form more closely. It will be best 

 simply to adopt some standard (say that of Clarke, but it makes 

 very little difference what), and to investigate hereafter the local 

 deviations from it. These deviations seem to be larger and 

 more extensive than used to be supposed, the station errors in 

 latitude and longitude being at least quantities of the same order 

 as the variations of elevation. 



We mention, in passing, the investigations of Fergola, based 

 on observations at Pulkowa and Greenwich, and leading to a 

 suspicion that the axis of the e.arth is slightly changing its posi- 

 tion and shifting the place of the Poles on the earth's surface. 

 Operations have been organised to determine the question by 

 co-operation between difterent observatories in nearly the same 

 latitude, but widely differing in longitude. 



Nor ought we to pass unnoticed an elaborate ])aper by Kap- 

 teyn, of Groningen, on the determination of latitude by a 

 method depending upon time-observation of stars, at equal 

 altitudes, though in widely different parts of the sky ; the stars 

 being so selected that all errors of star-place;, instrument, and 

 clock, are almost perfectly eliminated. In the sai.e connection 

 we ought to mention also the new equal-altitude instrument, 

 the Almucan'ar, invented by Chandler, of Cambridge, and his 

 development of the method of determining time by its use. It 

 may possibly supersede the transit instrument for this purpose, 

 as he seems to expect, though we think it hardly likely. 



Rapid progress has been made in determining the difference 

 of longitude between all the principal parts of the earth. There 

 now remain very few stations of much importance which have 

 not their longitude from Greenwich telegraphically settled 

 within a small fraction of a second. In Europe Albrecht has 

 combined into a consistent whole all the different data for more 

 than one hundred points. Our American system has been simi- 

 larly worked out by Schott, and is connected with the European 

 by no less than four different and independent cable-determina- 

 tions. South America is connected with the United States by 

 the recent operations of our naval officers in the West Indies 

 and along the eastern and western coasts of the continent ; and 

 with Europe by a cable connection between Lisbon and 

 Pernambuco, also effected by them. It is worth noting that 

 two large errors in European longitudes owe their detection to 

 American astronomers. The difference of longitude between 

 Greenwich and Paris was corrected by our Coast Survey in 

 1872 to the extent of nearly half a second of time, and our naval 

 officers in 187S showed that the then received longitude of 

 Lisbon was 8-545. too small ! It is a less surprising fact that 

 an error of 35s. was found in the longitude of Rio. 



Our navy has also determined an important series of tele- 

 graphic longitudes along the eastern coast of Asia and through 

 the East Indies. The French have been doing similar work m 

 the same regions, especially in connection with the transits of 

 Venus ; and the English have determined a large number of 

 longitudes in India. These Asiatic longitudes have been 

 recently connected with Australia and New Zealand by English 

 astronomers, and a telegraphic longitude connection has been 

 effected down the eastern coast of Africa fro u Aden to the 

 Cape ; so that now it jis perfectly practicable, if it is desirable, 

 to have one standard of time in all the civilised world. 



A word perhaps is here in place as to this question of standard 

 time and the beginning of the day. The .adoption by our rail- 

 roads of the system of standards differing from Greenwich time 

 only by entire hours has, I think, been admittedly a great step 

 in advance, as regards public convenience and safety in tra- 

 velling. At a few points, where standard and local time happen 



