590 



NA TURE 



[April 21, 1892 



about 427 days. In the Monthly Notices for March, Prof. New- 

 comb contributes a paper on the " Dynamics of the Earth's Rota- 

 tion," in which this result is mentioned with reference to the 

 periodic variations in latitude. By dynamic principles the ratio 

 of such a rotation to that of the earth's revolution " should be 

 equal to the ratio of her polar moment of inertia to the difference 

 between the equatorial and polar moments." This gives a time 

 of rotation of 306 days. Mr. Chandler's result, as Prof. New- 

 comb says, "at first sight seems in complete contradiction to 

 these principles," and he is led to inquire into the theory which 

 assigns the time of rotation. The present paper is the result of 

 such an investigation, and he finds that two defects have made 

 themselves apparent — "namely, the failure to take account of 

 the elasticity of the earth itself, and of the mobility of the ocean." 

 If the earth be considered first of all to be rotating as a homo- 

 geneous spheroid covered by an ocean of the same density as 

 itself, the axes of rotation and figure would of course be perfectly 

 coincident. By supposing a slight displacement of the axis of 

 rotation of o""20 in the case of our earth, he estimates approxi- 

 mately one-fourteenth of this as the movement of the axis of 

 figure in consequence of the shifting of the ocean. As two- 

 sevenths are required by Mr. Chandler's results, "the ocean dis- 

 placement only accounts for one-lourth of the difference." Since 

 the remainder must be attributed to the elasticity of the earth, 

 he inquires into the rigidity that our planet must have, so that 

 the displacement of the axis of figure may be two-sevenths that 

 of the axis of rotation : the result of the inquiry is to find that 

 a rigidity greater than that of steel must be assigned to it. The 

 effect of viscosity, he mentions, makes the normal pole move slowly 

 and continuously towards the revolving one, so that in time 

 they would meet if they were not acted upon occasionally by i-ome 

 opposing forces. The pole of rotation, according to Chandler's 

 period, makes six revolutions in seven years, and Prof. New- 

 comb investigates the effect of an "annually repeated cause" 

 that might produce such a change in the position of the earth's 

 axis. This effect, as he points out, would be cumulative for one- 

 half the period of seven years, and as the displacement is small, 

 a comparatively minute disturbing force can be looked for. Basing 

 his calculations on Chandler's period, he finds that such an effect 

 can be obtained, for, "if the winters in Siberia and in North 

 America occurred at opposite seasons, we should have no diffi- 

 culty in accepting the sufficiency of annual falls of snow to 

 account for this anomaly." 



RECENT ADVANCES IN PHYSICAL 

 CHEMISTRY} 



TN its course of development from a descriptive into a rational 

 science, chemistry has, in a tolerably regular series of 

 changes, passed in turn through periods of more special and 

 of more general interest. While the gathering together of 

 empirical facts proceeds in quiet, steady work, little troubled 

 by minor and rapidly decided differences of opinion, it is regu- 

 larly noticed, upon the other hand, that more generalizing ideas, 

 brought forward for the purpose of a rational comprehension 

 and unifying of this material, obtain only in the rarest cases a 

 kindly, immediate reception. On the contrary, the reaction 

 which such things at first call forth is almost always a more or 

 less violent opposition, its precipitate is to be sought out upon 

 the filter of the scientific literature of the time, there coming 

 afterwards to our view, in the text-books, only the clear filtrate 

 of the pure results. This has scarcely ever appeared more 

 strikingly than in the fall of the phlogiston theory : the perio- 

 dicals and books of the last century resound again with the 

 strife of the opponents, and often enough were the moral qualities 

 of the newer party attacked when the opposed argument-; became 

 threadbare ; whereupon from the attacked party a correspond- 

 ing reply was never lacking. The intellectual combat died 

 away but slowly, until the new territory was occupied in common 

 in peace and harmony. We have lived through a similar 

 experience in the change from the electro-chemical theory to 

 the substitution-theory, in the transfer from the idea of equi- 

 valents to that of molecular quantities, in the transformation of 

 the radical theory into the theory of types and structure. Even 

 the younger men among us lemember the strong opposition 

 with which was greeted at its first appearance that idea of the 



I Address delivered before the united Sections of Physics and Chemistry 

 at the yearly meeting of German Men of Science and Physicians at Halle^ 

 September 24, 1891, by Prof. W. Ostwald, Ph.D., of Leipzig. 



arrangement in space of the atoms in molecules, which now 

 occupies so many investigators. 



So it is a bloody field, whose present condition I have under- 

 taken to represent to you to-day. Do not fear that I shall bring 

 the uproar of conflict into this hour of peaceful looking back- 

 ward and forward. I have rather called up these recollections 

 in order to awaken in you the consciousness that this strife, 

 which has indeed not been wanting in the more recent years of 

 the development of general chemistry, is no abnormal pheno- 

 menon, possibly called forth by an unusual inferiority of the 

 newly appearing general ideas or of their defenders, but that it 

 is only a question of the normal birth-pains which unavoidably 

 accompany the appearance of important generalizations. 



But before taking up connectedly these newer and newest 

 things, it will be in place to cast a glance over the development 

 of those fields whose progress has been of a steady nature. 



First, as concerns the atomic weights. The investigations 

 which have been carried on for some years by American and 

 English investigators — Cooke and Richards, Morley, Lord 

 Rayleigh, Noyes, Dittmar, and others — upon the relation be- 

 tween hydrogen and oxygen, have not yet been brought to a 

 close. While most of the determinations have united to indi- 

 cate that the ratio of the atomic weights of these elements is 

 I to 15 "87, thus differing about 08 per cent, from the previously 

 assumed value i to i6"00, yet by means of a well-thought-out 

 method. Kaiser has found first 15 '945, while he has now just 

 announced that the most probable value is the old I to i6'oo. It 

 is remarkable that the efforts of so many investigators to determine 

 this fundamental constant accurately to within one part per 

 thousand have not yet met with a generally-accepted success. 



In this connection are to be mentioned the discussions, which 

 have been held upon the question as to the practical unit for the 

 atomic weights, whether 0=i6'ooor 15 '96 should be employed. 

 This is not the place to test the grounds adduced on both sides. 

 Perhaps it may be possible, with the present stricter organiza- 

 tion of our Society, to form a commission which shall subject 

 the question to a general examination, and which, by the stand- 

 ing of its members, shall be endowed with sufficient authority to 

 insure to its decision some prospect of general acceptance. 



The question as to the connection and significance of the 

 numerical values of the atomic weights has made no progress 

 of importance since the fundamental researches of Lothar 

 Meyer and Mendeleeff. Indeed, speculations do not cease in 

 the direction given by the assumption of a compound nature of 

 the elements, yet I know of none for which I could dare 

 prophesy growth and development. Steady work in the 

 revision of the numerical values of the atomic weights has 

 been patiently prosecuted. I need mention especially only the 

 close of the researches of the untiring Seubert upon the metals 

 of the platinum group ; and we should recognize with great 

 thankfulness the devotion with which this work, so thankless in 

 itself, has been carried through. 



No new elements of importance have come recently to light. 

 Although in the garden of the "rare earths" many a blossom 

 has appeared, there fail as yet any real fruits. 



In the theory of gases the investigations continue according 

 to the general equation of condition [Zustandsgleichung), in that 

 the recognition is steadily breaking its way, that the nearest 

 entrance to the theory of liquids leads necessarily over the 

 critical point. The kinetic hypothesis, which was greeted in its 

 time with so much sympathy, and has enjoyed such careful 

 attention, is showing itself here essentially unfruitful, since the 

 two main principles of the theory of van der Waals, to which 

 the immediate future undoubtedly belongs, are independent of 

 the kinetic hypothesis. In fact, neither the assumption that 

 only the space which is tiot filled with the substance of matter 

 follows Boyle's law, nor the assumption that this matter pos- 

 sesses still some energy of reciprocal action, necessitates any 

 definite representations whatever in the sense of the kinetic 

 hypothesis. 



Among the experimental researches upon these relations are 

 especially to be mentioned those of Ramsay and Young. The 

 relation determined by them, that within a very wide range the 

 equation p{v ~ b) = /T is true, or that the co-volume, b, is 

 independent of the pressure, is one of the few general facts 

 which are leading us to a more accurate knowledge of the general 

 equation of condition. 



In solving the task of finding a theory of the liquid condition, 

 we shall have to seek other properties, which show themselves 

 to be. here subject to the more simple laws. As yet but few 



NO. II 73, VOL. 45] 



