270 



In the following we publish the results of the measurements with 

 these derivatives. 



The determination of the specilic gravity was made either by means 

 of the pycnometer, or bj means of volumeters especially constructed 

 for that purpose, and which were previously accurately calibrated. 

 If both these methods could not be applied, the determinations were 

 made by the aid of a hydrostatic method, which some lime ago 

 was developed by the first-named of us originally for the purpose 

 of measuring the densities of molten salts and liquid niagmata at 

 very high temperatures, and which will be described in detail on 

 a future suitable occasion. By preliminary experiments and by com- 

 jKirison of the results thus obtained with those collected by other 

 methods, the applicability and reliability of the method were proved 

 and the degree of accuracy eslablislied ; the last appeared to be no 

 less than that reached by the usual way of measuring. 



§ 2. 



