September 10, 1886.] 



SCIENCE. 



235 



a cavernous condition of the Trenton in Ohio, then 

 Dr. Orton's terrace structure of the top of the Tren- 

 ton becomes of value as indicating slopes in the gen- 

 eral plane of the cavernous part of the formation. 

 By this I mean to indicate the probability that the 

 vs'hole formation is not cavernous to an equal extent 

 throughout (from top to bottom), but that certain 

 members of the mass are more soluble than the rest. 

 In Pennsylvania the Trenton itself is not cavernous 

 on a grand scale : our sinking springs are along the 

 outcrop of the passage-beds at the bottom of the 

 Trenton and Bird's-eye and top of the calciferous. 

 The whole formation in front of the Alleghany 

 Mountains is between six and seven thousand feet 

 thick. The uppermost thousand feet is very compact 

 and non-mangesian ; the underlying mass is com- 

 posed of alternate layers of limestone and dolomite, 

 with some low-lying calcareous sandstone groups. 

 Dr. Orton reports the formation in Ohio ' magnesian, 

 of a fair character throughout most of its extent,' 

 but ' somewhat siliceous in some of the drillings.' It 

 will be an important item of investigation, how far 

 the cavernous horizon in Ohio corresponds to that in 

 Pennsylvania, where the formation is ten times as 

 thick as in Ohio. Dr. Orton inadvertently remarks 

 (p. 18) that ' there is no warrant for assuming its 

 universality as a limestone ' under the country be- 

 tween middle Ohio and middle Pennsylvania. But I 

 am sure that he will revise the remark when he re- 

 flects that a formation which is ' universally lime- 

 stone ' from Tennessee to the Manitoulin Islands in a 

 north and south direction, and is universally lime- 

 stone along the whole Appalachian belt from Ala- 

 bama to New York, cannot possibly be any thing else 

 than limestone under the intermediate region of the 

 bituminous coal-measures. If there is any reasoning 

 from the exposed to the concealed in geology, all 

 geologists must feel sure — quite sure — that the 

 lower Silurian formation No. II. must underlie 

 Wheeling and Pittsburgh as a limestone formation, 

 non-magnesian at top, magnesian at middle and bot- 

 tom, at least two thousand if not three thousand 

 feet thick, and at a depth of, say, ten thousand feet 

 beneath the present surface. 



But I have been led on to a much greater length 

 than I expected, by the importance of the subject, 

 to the new gas and oil industry of Ohio. I cannot 

 trespass longer on your space with the obvious appli- 

 cations of what I have adduced above to the vexed 

 questions of local capriciousness, etc., in the new oil 

 and gas field. J. P. Lesley. 



Philadelphia, Sept. 1. 



The law of volumes in chemistry. 



The questions regarding the so-called molecular 

 weights and volumes of liquids and solids, which are 

 now attracting the attention of chemists, can, I 

 think, be better understood if we keep in mind the 

 principles enunciated by the writer in 1853, that 

 *' the doctrine of chemical equivalents is that of the 

 equivalency of volumes," and that "the simple rela- 

 tions of volumes which Gay-Lussac pointed out in 

 the chemical changes of gases apply to all liquid and 

 solid species ; " so that " the application of the atomic 

 hypothesis to explain the law of definite proportions 

 becomes wholly unnecessary." In further illustration 

 of this view, it was said in 1867 that "the gas or 

 Vapor of a volatile body constitutes a species distinct 

 from the same body in a liquid or solid state ; and 



the liquid and solid species themselves often [prob- 

 ablj^ always] constitute two distinct species of differ- 

 ent equivalent weights." From this it follows that 

 freezing, melting, and vaporization are chemical 

 changes. The union of many volumes of a vapor or 

 gas in a single volume of a liquid or a solid is a jjro- 

 cess of chemical combination, while vaporization is 

 chemical decomposition. Such decomposition is 

 either with or without specific difference, and ex- 

 amples of these two modes are seen respectively in 

 heterogeneous dissociation and in integral volatiliza- 

 tion, which latter is the breaking-up or dissociation 

 of a polymeric species into simpler forms having the 

 same centesimal composition. Both of these pro- 

 cesses are subordinated to the same laws of pressure 

 and temperature, and involve similar thermic changes 

 in the relations of the bodies concerned. In this 

 enlarged conception of the chemical process we find 

 a solution of the problems above named, and an ex- 

 planation of the distinction which has been made 

 laetween ' the chemical molecule ' and ' the molecule 

 of the physicist.' That the latter has a much less 

 simple constitution than the former, as calculated 

 from the results of chemical analysis and from vapor- 

 density, has been long maintained alike on dynamical 

 and chemical grounds. It is discussed by the writer 

 in 1853 in the essay already quoted, entitled * The 

 theory of chemical changes and equivalent volumes,' ' 

 and again in the late paper of Spencer Pickering in 

 the Chemical neivs for November, 1885. 



If, then, as maintained by the writer, the law of 

 volumes is universal, and if the production of liquids 

 and solids by the condensation of vapors is a process 

 of chemical union giving rise to polymerids, the 

 equivalent weights of which are as much more ele- 

 vated as their densities are greater than those of the 

 vapors which combine to form them, the hypothesis 

 of atoms and molecules, as applied to explain the law 

 of definite proportions and the chemical process, is 

 not only unnecessary, but misleading. According to 

 this hypothesis, which supposes molecules to be built 

 up of atoms, and masses of molecules, the different 

 ratios in unlike species between the combining weight 

 of the chemical unit or molecule (as deduced from 

 analysis and from vapor-density ; H = 1.0) and the 

 specific gravity of the mass are supposed to repre- 

 sent the relative dimensions of the molecule. Hence 

 the values got by dividing these combining weights 

 by the specific gravity have been called ' molecular 

 volumes.' The number of such molecules required 

 to build up a physical molecule of constant volume 

 would, according to this hypothesis, be inversely a& 

 their size. If, however, as all the phenomena of 

 chemistry show, the formation of higher and more 

 complex species is by condensation, or, in other 

 words, by identification of volume, and not by juxta- 

 position, if? follows that the so-called molecular vol- 

 umes are really the numbers representing the relative^ 

 amount of contraction of the respective substances 

 in passing from the gaseous to the liquid or solid 

 state, and are the reciprocals of the coefficient of 

 condensation of the assumed chemical units. If 

 steam at 100° C. and 760 millimetres pressure, with a 

 formula as deduced from its density of H3O, and a 

 combining weight of 18, is converted into water at 

 the same temperature, 1,628 volumes of it are con- 

 densed into a single volume, having a specific gravity 

 of 0.9588, which at 4° C. becomes 1.0000. Water is 



1 See the author's ' Chemical and geological essays,' pp- 

 426^37, and, further, ibid., pp. 453-45b. 



