536 SCIENCE PROGRESS. 



cleaning " were allowed to stand a sufficient time to acquire 

 the temperature of the room and were then weighed " to 

 Tijo of a milligram. One source of error which may have 

 existed and apparently was not investigated sufficiently was 

 the tightness of the tap on the palladium tube, the palla- 

 dium practically being weighed in vacuo before and after 

 the experiment. Air might easily leak in as any one who 

 has had anything to do with the very best glass taps knows, 

 and when it is a three way stopcock the risk is greatly in- 

 creased. The connection of two of the pieces by ground 

 glass joints wanted careful testing, especially as the joints 

 seem to have been used free from lubricant of any kind. 

 This paper is unsatisfactory, therefore, although of fair 

 length, as it does not give precise information where it is 

 most required, but gives, instead of such, only general 

 statements. No arrangement seems to have existed 

 for that most fundamental of all such operations, 

 viz., testing whether the apparatus was air-tight to begin 

 with. 



Lord Rayleigh (13) used yet another gravimetric 

 method, he abstracted from weighed globes containing 

 hydrogen and oxygen a quantity of each gas and combined 

 them by successive explosions and then determined the 

 small volume of the residual gas and found its weight by 

 calculation. The loss of weight of the respective globes 

 after due correction for the change of volume consequent 

 on the changed internal pressure, and for the small residual 

 volume of one gas, gave the weights of the two gases which 

 entered into combination. The value thus derived is 

 o = 15*89 or H = i'oo692. 



The ratio of the respective volumes in which the two 

 gases combine to form water has been determined directly 

 by both E. W. Morley (14) and the author (15), but the 

 results arrived at are not the same, nor does either agree 

 with the result deduced by Leduc (16) from his determina- 

 tions of the densities of hydrogen and of oxygen and that 

 of the mixture of the gases obtained from the electrolysis of 

 strong caustic potash solution, which he seems to assume 

 contains the gases in exactly the proportions in which they 



