294 



NA TURE 



\_Aiigiist 9, 1877 



statement, "All gases contain the same number of mole- 

 cules ; " the molecule may then be formed — 



It may be by i atom, as Hg, Cd, &c. 



„ 2 atoms, as H, CI, O, &c. 



„ 3 „ „ Ozone. 



„ 4 » ,, I P, A, &c. 



What is there in this, M. Berthelot asks, more logical than 

 in his own method ? or in what may it be allowed to con- 

 stitute a modern chemistry in distinction to that of 

 Lavoisier and of Gay-Lussac ? 



In answer to M. Berthelot, M. Wurtz discusses in a 

 further communication the thermic considerations brought 

 forward by the former in his explanation of the 

 reciprocal reactions already alluded to of hydride of 

 copper with hydrochloric acid and peroxide of hydrogen 

 with other peroxides. M. Wurtz, although acknow- 

 ledging the value of these considerations, considers the 

 reasoning incomplete, by merely saying that hydride 

 of copper is an endothermic compound ; it would be 

 necessary to prove in addition why such bodies, having a 

 greater capacity of heat than their constituent elements, 

 can be formed or exist at all. He maintains that his 

 own ideas admit of the intervention in the thermic con- 

 siderations relative to the formation of such bodies as 

 peroxide of hydrogen, ozone, chloride of nitrogen, &c., 

 the work done in doubling the molecules of oxygen, Oj, 

 chlorine, CL, and nitrogen, Nj ; this work causing an 

 absorption of heat. He brings forward the ideas of M. 

 Favre regarding the formation of bodies with an absorp- 

 tion of heat and alludes to the idea of this latter chemist 

 of representing free oxygen as Oo and nascent oxygen as 

 O, the latter being more active m consequence of being 

 supplied with more heat from what he calls the " segre- 

 gation "of the molecule. M. Wurtz concludes that the 

 thermical reasoning instead of being opposed to the 

 atomic conception materially assists it. 



In passing to the iurther objections made by Berthelot 

 to expressing the reaction of potassium and hydrochloric 

 acid as — 



2HCl+K2 = 2(KCl)-f Ho, 



M. Wurtz explains it as a necessity to render it comparable 

 to the reaction — 



2HCI -H Zn = ZnClj + Ha, 



this representing 63-5 of zinc or two equivalents, having 

 doubled the equivalent of zinc, as also of certain other 

 metals for two reasons : firstly, to allow them to accord 

 with the law of Dulong and Petit ; and secondly, to 

 satisfy Avrogadro's law. M. Wurtz evidently considers M. 

 Berthelot in the position of almost wishing the abolition 

 of Dulong and Petit's law, and explains that although the 

 product of the specific heats into the atomic weights may 

 not always prove rigorously constant, still they are suffi- 

 ciently near, it being difficult to obtain one and the same 

 metal under conditions strictly comparable. He wishes 

 therefore to retain the law of Dulong and Petit as a check 

 for the determination of the atomic weights. The notation 

 of equivalents, he thinks, contains certain inconsistencies, 

 and complains that no direct response has been made by 

 its upholders to this point, which is really at the foun- 

 dation of the discussion ; they have only objected to 

 atomic notation as introducing vexatious complications 

 in expressing the reactions of mineral chemistry. 



To M. Berthelot's reproach that he has confounded the 

 notion of a hypothesis with that of a law, M. Wurtz 

 replies in the following sentence :—"Je le remercie de 

 cette le<;on de philosophic ; mais je ne crois pas en avoir 

 besoin." He admits, for his own part, his knowledge that 

 the notion of atoms and molecules is only a hypothesis, 

 one which it is allowable to make on the constitution of 

 matter, and essentially dependent on another, that of the 

 existence of the ether. M. Berthelot believes the atomic 

 hypothesis ill-founded, as atoms and molecules have 



never been seen, but for the same reason it would be as 

 difficult to imagine the ether. To reject this latter hypo- 

 thesis it would be necessary to adopt that of continuous 

 matter of differing degrees of density filling all space, 

 and M. Wurtz repeats that chemical notation, the point 

 in question, is independent of such hypotheses. 



The notion of atoms and molecules would have to be 

 replaced by that of infinitely small vibrating masses, and 

 at the basis of the notion of equivalent quantities lies the 

 same idea of finite particles. What is really necessary is 

 the choice of exact numbers to express the relative weights 

 of these particles by whatever name they may be called ; 

 according to M. Wurtz they are of two orders : isolated, 

 he calls them atoms ; combined, molecules. Is this, he 

 asks, an ill-delined idea .'' 



In a discussion like the present, which has existed for 

 so long, and which doubtless will still be continued, it is 

 extremely difficult to balance accurately the arguments 

 used by the upholders of the different theories. Although 

 many and forcible reasons have been brought forward by 

 both contending parties, we fear that no final victory has 

 been gained by either side. M. Berthelot objects to the 

 idea of molecules and atoms, but he evidently does not 

 wish to exclude entirely imagination and hypothesis from 

 scientific reasoning, and deems, as is probably the case, 

 that the fundamental conceptions of the two chemical 

 schools may not differ so much in that matter as perhaps 

 M. Wurtz at present imagines. 



The point on which the real difference seems to exist is, 

 in perceiving the true importance of such representative 

 conceptions, and placing them in the position they should 

 occupy in human knowledge. J. M. T. 



THE GREENLAND FOEHN^ 



ONE ot the chief peculiarities of the meteorology ot 

 the Arctic regions, and particularly of West 

 Greenland, is the great variability of the temperature in 

 the cold part of the year. There may not only be a very 

 considerable variation in the average monthly temperature 

 from year to year, but sudden changes from the severest 

 cold to fresh weather, and vice versa, often occur several 

 times in the course of the same month. 



Dr. Pfaft' has carried on meteorological observations 

 at Jacobshavn for twenty years, and these show that the 

 average temperature of 1872 was —87° C, and of 1863 

 - 316'^, a difference accordingly of almost 23° — an almost 

 inconceivable variableness to us West- Europeans ; being, 

 for instance, nearly as great as the difference between the 

 coldest winter month and the warmest summer month at 

 Copenhagen within the same period. The observations 

 referred to also exhibited the most remarkable instances 

 of daily variations. In February, i860, the thermometer 

 rose on three different occasions more than 25" C. in the 

 course of twenty-four hours. 



These singular and sudden rises of temperature almost 

 always stand in connection with a veering of the wind to 

 south-east and east. It may appear very surprising, that 

 the temperature rises with the wind blowing from the high 

 land in the interior of Greenland, which is covered with 

 eternal snow and ice. We need not, therefore, be 

 surprised that old authors have endeavoured to explain 

 this phenomenon by supposed volcanoes in action, or 

 even by a comparatively very mild climate in the interior 

 of Greenland — an hypothesis which it is, however, quite 

 impossible to maintain on meteorological grounds. For 

 every continent in high latitudes must necessarily, from 

 the radiation of heat, be colder in its interior than at the 

 coast where the sea makes the climate milder. 



A glance at the map shows that Greenland lies between 

 regions of the earth where, especially in winter, the 

 temperature is exceedingly different. " To the west and 



> Abstract of a paper by HolTmeyer in the Danish Geographical Society's 

 youmai. Part I., transUted tiom Naturen of June, 1S77 iChtistianiaJ. 



