in the Twenty Years before 1895 67 



wire for fractions of a gramme, and of brass or silver wire 

 for greater weights. The system is such that any weight 

 up to 10 grammes, increasing by steps of 0-05 gramme, can 

 be added. It is thus possible, by making the first reading 

 when the instrument is loaded so as just to be immersed to 

 1(3 west division (o mm.) of the stem, to make a series of 

 twenty-one independent determinations of the weight of 

 twenty-one different volumes of the same liquid in a very 

 few minutes. If the liquid is replaced in the cylinder by 

 r of the same temperature, twenty-one determina- 

 tions of the weight of the same twenty-one volumes of distilled 

 r of the same temperature can be made in as short a 

 time, and we have as the result twenty-one perfectly indepen- 

 dent determinations of the specific gravity of the liquid, that 

 is, of the ratio of its density to that of distilled water of the 

 same temperature; and the accuracy of each determination 

 depends on nothing but the accuracy with which the original 

 weii,- :ried out that is to say, it depends 



on the operation, which is capable of being performed with 

 greatest precision in the laboratory. In actual practice 

 steps of o-i gramme, and I aim at having at least nine 

 separate observations both in the liquid and in distilled water. 

 It never happens that the successive readings in distilled 

 r are identical with those in the liquid, but by repeated 

 imn. i di-tjll.-d water the stem is accurately calibrated, 



so that a correction can with safety be made for the difference 

 of one or two millimetres between them. We then have a 

 series of scale reading, and opposite each a pair of weights 

 ig the v. of these identical volumes of the liquid 



of di-tillrd water, and tlic ratio of each pair gives the 

 specific gravity of the liquid at the common temperature. 

 n< i difficulty, when working in the oireumstances 

 Lone ^uitable for determination^ of the kind, in 

 identity <>f temperatures within O'I C. 

 ill ordinary purpos not necessary to make a 



ill'd water alonjj with each sample of 



sea- water or other liquid under examination. When a sufficient 

 number of * :ons have been made in distilled 



5-2 



