/;/ the Twenty Years before 1895 



the fifth decimal place, and the individuals of each pair depend 

 on perfectly distinct sets of weighings, and are therefore quite 

 independent. 



It may safely be asserted that, working in this way, the 

 :ific gravity of a sea-water or similar solution can be deter- 

 mined with a probable error of not more than I in the fifth 



ill j>l ice. In a water whose specific gravity is 1-03000, 

 i in the fifth decimal place represents -^^ of the whole solid 

 contents; so that, by the careful use of the hydrometric 

 method, the salinity to one part in 75,000 of water, or differences 

 of i grain per gallon, can be determined; and it has proved 

 itself of great use in general chemical practice, especially in 

 cases of pollution of streams. 



It has been shown that the sperinV ^r.ivitv of a sea-water 



be determined with the greatest possible accuracy with 

 the hydrometer, and, in reporting on a water, tin- i> the first 



tnndamrntal n-sult to be stat-. l. It is an absolute value 

 depending onlv on tin- ar< nra< v uith whirh the weight of the 

 livdrom. been detnminrd. and i om all other 



errors. In order that observations on different Wfttfefl may 



