On the Hjdromeler. 159 



Hrengths of fpirituous liquors have been devifed, applicable 

 ill a grnfs manner to a general ufe, it i;5 well known tliat no 

 method admits of rearaccuracy bnt tliatof the fpeci tic gra- 

 vity. The weights of an equal bulk of water and pure fpirit 

 differ from one"another by at lead a fixth part of the weight 

 of the former; whence it is obvious, that when thofe two 

 fluids arc mixed together, the compound muft have feme 

 intermediaie fpecitlc gravitv, approaching nearer to that of 

 water or pure fpirit, as the former or the latter is tlie more 

 predominant ingretlienl. 



" Were it not for a certain effeft attending the mixture 

 •of water and fpirit, which has been called their mutual pe- 

 netrati(m, the fpecitic gravity of thefe compofitions, in a 

 given decree of heat, would be fimplv in the arithmetical 

 proportions of the quantity of each of the fluids entering into 

 them. 



" But whenever different fubftances, which have a flrong 

 tendency to unite looiether, are mix€d, the refulting compound 

 is found to occupy lefs fpace than the fubllances forming it 

 held in their i'eparate (tate; wherefore the fpecilic gravity of 

 i'uch compounds is always greater than would be given by a 

 Umple calculation from the volume of their ingredient.-*. 

 Though it be a general fact, that fuch a decreafe of bulk 

 tikes i)laces on the mixture of fubllances which have a che- 

 niical attraction for each other ; yet the quantity ot this di- 

 ininution is ditl'erent in them all, and, under our prefcnt ig- 

 norance of the intimate compofition of bodies, can be deter- 

 mined by experiment only. To afcertain, tlierefore, the 

 quantity and law of the condenfation refulting from this 

 mutual penetration of water and fpirit, was the firlt objeC;t 

 to which the following experiments were direfred. 



" All bodies, in general, expand by heat : but the quan- 

 tity of this expanfion, as well as the law of ils progreffion, 

 ?.re probably not the fame in any two fubftances. In water 

 and fpirit they are remarkably different. The whole expan- 

 fion of pure fpirit, from ^o'^ to ico^ of Fahrenheit's thermo- 

 meter, is not lefs than i-i^th of its whole bulk at 33"; 

 whereas that of water, in the fame interval, is only I-I45th 

 of its bulk. The laws of their expanfion are ftill more dif- 

 ferent than the quantities. If the expanfion of quickfilver 

 be, as ufual, taken from the ftandard (our thermometers 

 being conftrucled with that fluid), the expanlion of fpirit 

 is, indeed, progrcflively incrtafiug with refpedl to that fland- 

 ard, but not nmch lb within the above-mentioned interval ; 

 whilfl water kept from freezing to 30', v.hich may cafily be 

 done, will abfolulely contract »<> it is heatui, for tea or more 



degrees, 



