*25S ^"^ THE CONSTITUTION OT MIXED GASES, SfC^ 



Statement of As the detail of experiments will be bed underftood and 



certain laws ^j^^jj. application feen, if the laws of principles alluded to be 



pievious to their .' . . ' ' 



fundamental ex- kept in view, it ma}' be proper here to ftate them ; though it 

 peiunents. jnud not be underftood that they were proceeded upon hypo- 

 thetically in the diredion of thofe experiments. On the con- 

 trary, the firft law, which is as a mirror in which all the ex- 

 periments are beft viewed, was lajl deteded, and after all the 

 particular fads had been previoufly afcertained. 

 f. Mixed elaftic !• When two elaftic fluids, denoted by .^ and 5, are mixed 

 fluids do not together, there is no mutual repulfion amongft their particles ; 

 rcpe eac o er. ^j^^^ .^^ ^j^^ particles of A do not repel thofe of £, as they do 

 one another. Confequently, the prelTure or whole weight 

 upon any one particle arifes folely from thofe of its own 

 llind. 

 a. The fteam of 2. The force of fleam from all liquids is the fame, at equal 

 any liquid, at diflances above or below the feveral temperatures at which 



any given num- , , ., • i • i ■ /• • , r . 



ber of (iegrees they boil in the Open air : and that force is the lame under any 

 fiom its boiling prefTure of an other elaftic fluid as it is in vacuo. Thus, the 

 fame 'f.s^ that of ^orce of aqiieous vapour of 212® is equal to 30 inches of 

 any otlier liquid mercury; at 30° below, or 182°, it is of half that force; 

 number^o/ ^"^ ^' ^^'^ above, or 2520, it is of double the force ; fo like- 

 egrees, the wife the vapour from fulphuric ether which boils at 102'^, then 

 fupporting SOinches of" mercury, at 30° below that temperature 

 it has half the force, and at 40° above it, double the force; 



fame way from 

 its boiling point, 



and fo in other liquids. Moreover, the force of aqueous 



vapour of 60° is nearly equal to half inch of mercury, when 



admitted into a torricellian vacuum ; and water of the fame 



temperature, confined with pcrfedly dry air, increafes the 



elafticity to juft the fame amount, 



3. Evaporation 3. The quantity' of any liquid evaporated in the open air is 



nuTfa "r'^thc"* '^''■^^^y ^^ the force o\' fteam from fuch liquid at its tempera- 



£)rce of the luFC, all Other circuinftances being the fame. 



^'"T,', , .. 4- All elaftic fluids expand the fame quantity by heat : and 



/-. All ciafhc ,. ^ . ,-i/- ,, , Y- 



fl 'litis cxoand this expanuon is very nearly in the iame equable way as that or 



';-4u.i!iy by heat, mercury; at leaft from 32° to 212°.— It feems probable the 

 expunfion of each particle of the fame fluid, or its fphere 

 of influence, is dire^ly as the quantity of heat combined with- 

 it ; and confequently the expanfion of the fluid as the cube 

 of the temperature, reckoned ffom the point of total priva- 

 tion. 



Having 



