Log. ^^44^ = Log. 11-5 + Log. c» h^ - Log. a^ d^ = 1-06070 



On Cohesion. 89 



Log. li^^ = Log. 11-5 + Log. c' i«-Log. J' a^=l-0G07O 

 +6-9S676-84142 = --19396 = Log. -6397 



1-5 r^ 



+ 6'r2397-7-l8642=--00175 = Log.-996 



■r^ = 1'436 : 1 : : specific grav. of composition : spec, gravitv 

 tin 1-436 X 7-2914 = 8-8736338 = specific gravity of the com- 



pound ——-.— ==^ = — - - - = f^= 1-436 : I : : cohesion 



of tin to cohesion of compound. 



The specific gravities found in the two last examples agree 

 exactlv with those deduced from actual experiment. The truth 

 of the principle on which thev are calculated may therefore be 

 considered as demonstrated. The cohesions of bodies, particularly 

 when small, are exceedingly difficult to ascertain. A plan which, 

 however, I have lately adopted, will, I hope, enable me to obtain 

 something satisfactory on this head ; and I have no doubt but 

 the result will amply confirm the truth of my hypothesis. In 

 fact, the calculation of the specific gravity being founded on the 

 very same principle as that of the cohesion, (viz. that cohesion is 

 inversely as the scjuare of the distance,) the truth of the one is a 

 proof of that of the other. 



From the formulae given above may be calculated the specific 

 gravity and cohesion of a chemical compound of any two sub- 

 stances, the specific gravities and cohesions of which are known; 

 they mav therefore be extensively applied in tlie practice of me- 

 tallurgy as well as chemistry. 



In a future number of the Philo^sophical Magazine I shall give 

 various formuhe for calculating the specific gravities and cohesions 

 of compounds formed by any given numbers and proportions ot 

 different bodies, and for finding the proportions in which any 

 number of bodies must be combined, in order to produce a given 

 specific gravitv or cohesion ; as well as various new methods ot 

 a"5certainin!X tlio cohc-iions of bodies. By means of these for- 

 mula? and those already given, the portion of alloy contained in 

 gold or silver may be found at once from their specific gravity; 

 and the proportion in which any compound metal, as brass, &c. 

 is compounded, from the specific gravity of such metal. 



XVII. Ob- 



