Jt^o On the Hydrometer. 



" Every table confifts of eight columns, and there are twd 

 tables for every degree of heat. In the firft column of ihejirjl 

 of the two tables are given the proportions of fpirit and water 

 by weight, lOO parts of fpirit being taken as the conftant 

 number, to which additions are made fucceffively of one part 

 of water, from T to 99 inclufively : the firll column in the 

 fecond table has ico parts of water for the conilant number, 

 with the parts of fpirit decreafing fucceffively by unity, from 

 100 to 1 inclufively. ■ 



" It muft be obferved, that each of thefe tables, occupy- 

 ing one page, is divided in the middle for adapting it more 

 conveniently to the fizc of the paper; but the whole of each 

 page is to be confidercd as one contiuned table. The lecond 

 column of all the tables gives the fpecific gravities of the cor- 

 refponding mixtures of fpirit and water m the firft column, 

 taken from the table of fpecific gravities in the Supplementary 

 Report, the intermediate fpaces being filled up by interpola- 

 tion. In the third column, 100 parts by meafure of pure 

 fpirit, at the temperature marked at the top of every feparate 

 table, is afiumed as the conllant ftandard number, to which 

 the refpeftive quantities of water by meafure, at the fame 

 temperature, are to be proportioned in the next column. 



*' The fourth column, therefore, contains the proportion 

 of water, bv meafure, to 100 meafurcs of fpirit, anfwcring to 

 the proportions by weight in the fame horizontal line of the 

 firft column. The fifth column fliows the number of parts 

 which the quantities of fpirit and water, contained in the 

 third and fourth columns, would meafure when the mixture 

 has been completed ; that is, the bulk of the whole mixture 

 after the concentration or mutual penetration has fully taken 

 place. The fixth column, deduced from the three preceding 

 ones, gives the effefts of that concentration, or how much 

 fmaller the volume of the whole mixture is, than it would 

 be -if there was no fuch principle as the mutual penetration. 

 The feventh column Ihows the quantity of pure fpirit by 

 meafure, at the temperature in the table, contained in an 

 hundred meafures of the mixture laid down in the fifth co- 

 lumn." 



From this account it will be feen, that every mixture of 

 pure fpirit and v/ater poffible to be made, is analyfed fo clearly 

 at everV' temperature, as to render it a matter of no great dif- 

 ficulty to demonftrate, at a given temperature, all the grada- 

 tions of ftrenpth which the hydrometer fliould indicate. The 

 inode in which this has been done I fliall now explain. 



The table which Mr. Gilpin has calculated for the tem- 

 perature of 55, is that which I have chofeu, conceiving it, 

 y for 



