28 



THE ATOMIC WEIGHTS. 



alone was read. The results for the weit,^ht in grammes, at latitude 45°, 

 of one litre of oxygen are as follows : 



General mean of all three series, 1.42896, ± .000028. 



Morley himself, for experimental reasons, prefers the last series, and 

 gives it douhle weight, getting a mean densit}' of 1.42900. The differ- 

 ence between this mean and that given above is insignificant with ref- 

 erence to the atomic weight problem. 



In the case of hydrogen, Morley's determinations fall into two groups, 

 but in both the gas was prepared by the electrolysis of pure dilute sul- 

 phuric acid, and was most elaborately purified. In the first group there 

 are two series of measurements. Of these, the first involved the reading 

 of temperature and pressure by means of a mercurial thermometer and 

 mano-barometer. In the second series, the gas was delivered into the 

 weighing globes after occlusion in palladium ; it was then kept at the 

 temperature of melting ice, and onl}^ the syphon barometer was read. 

 In this group the hydrogen was possibl}'' contaminated with mercurial 

 vapor, and the results are discarded by Morley in his final summing up. 

 For present purposes, however, it is unnecessary to reject them, for they 

 have confirmatory value, and do not appreciably affect the final mean. 

 The weight of one litre of hydrogen at 4-5° latitude, as found in these two 

 sets of determinations, is as follows : 



* Correction applied by Morley to all his series, for a slight error, g^o^o o > ^" *-'^^ length of his 

 standard metre bar. 



