March 23, 1900.] 



SCIENCE. 



445 



periment furnishes us for this relation in 

 the case of the vapor of mercury a higher 

 value than in most gases. This ratio is 

 one and two- thirds, that is, it is exactly the 

 figure which is demanded by the kinetic 

 theory of gases for a gas which contains 

 a monatomic molecule, where the atomic 

 energy of the molecule can be neglected 

 when compared with that of the molecule 

 as a whole. The velocity of sound in the 

 lately discovered gases, argon, helium, neon, 

 xenon and krypton, has also been found to 

 correspond to monatomic molecules. This 

 knowledge stands further in beautiful har- 

 mony with the chemical properties of these 

 elements, whose atoms— apparently without 

 fiffinity — appear unable to enter into any 

 kind of combination. They seemed doomed 

 to eternal solitude. 



We now come to tlie first of the three 

 problems which we have proposed for our 

 consideration to-day. The question of the 

 indestructibility of matter can best be intro- 

 duced by recalling the investigations of the 

 distinguished Belgian chemist, Stas, who 

 attained an exactness in his work which 

 has excited the admiration of all succeed- 

 ing chemists. His investigations espec- 

 ially reveal where the experimental pos- 

 sibilities in this field find their limit. A 

 closer view of his work would unfortunately 

 compel us to enter upon a series of dry 

 studies of figures. "We will, however, take 

 one example from among these. In order 

 to prove our law, Stas prepared synthet- 

 ically three quarters of a kilo of silver 

 iodid, a quantity which the analytical 

 chemist would consider enormous, and he 

 found this weighed only fourteen and one- 

 half milligrams less than the weight of 

 the constituents of the compound. This 

 is an accuracy reaching one fifty-thou- 

 sandth part of the whole quantity. How 

 extraordinarily close to complete agree- 

 ment these figures lie may be judged when 

 one considers that in our ordinary gravi- 



metric methods, using perhaps a gram of 

 substance, an error of one milligram may 

 certainly be looked upon as small. This is 

 an error of a one-thousandth of the whole 

 quantity used. 



As further experimental contributions to 

 the law we are considering the work of 

 Kreichgauer and that of Landolt is interest- 

 ing. These investigators have carried on 

 chemical observations in fused glass tubes 

 in order to decide, by most careful weigh- 

 ing, these two questions : whether in a re- 

 action, a ponderable portion of ether dis- 

 appears or is added to the substances used ; 

 and whether the products of a reaction 

 are influenced in exactly the same way by 

 gravity as are the factors which enter into 

 the reaction. Kreichgauer's experiments 

 were calculated to detect a change in weight 

 which would have amounted to one twenty- 

 millionth of the mass present, but even this 

 minute change of weight was not detected. 

 In Landolt's experiments it was also im- 

 possible to detect any change in weight, 

 although he did not consider the possibility 

 of such a change absolutely excluded, chiefly 

 because the variations, which were consider- 

 ably less than one-tenth of a milligram, 

 were always in the same direction. 



In more recent times Ramsay and Ray- 

 leigh have carried out extremely accurate 

 experiments. These distinguished scien- 

 tific observers at first set before themselves 

 merely the problem of determining, with the 

 greatest possible accuracy, the weight of a 

 few gases, among others that of nitrogen ; 

 but in the course of these investigations 

 they came to the most unexpected results, 

 for they were led to the discovery, and 

 later to the separation of the unknown 

 constituents of the air, argon, xenon, etc., as 

 already mentioned. In such ways, an ever 

 increasing perfection leads to ever more 

 accurate results. And if it be true that in 

 all investigations of this kind we must be 

 denied the possibility of reaching the abso- 



