186 Mr. Emmett on the [Sept. 



posed to be reciprocally in the duplicate ratio of the distance, 

 and which in masses produces gravity. Since then this latter 

 force is known to exist, and we have not the most trivial indica- 

 tion of any other, we may fairly infer that this force alone is 

 concerned in producing the attraction of cohesion, and that the 

 results obtained by help of the above propositions minutely agree 

 •with what we observe to attain in nature, is proved by the fol- 

 lowing computation : Suppose two solid spheres, the diameter of 

 each being one inch, to be placed in contact with each other ; 

 let the weight of each be 1000 grs. and the force of cohesion to 



be ,^,--^,, th of a grain ; of the same matter let a cylinder of one 

 inch in diameter be formed, its component particles being equal, 

 and having a diameter = th of an inch ; the weight of 



each particle becomes 7 — ^ gr'. = th of a sr. 



{1000000}' ® 1000000000000000 = 



and by prop. 1, the cohesive force between two adjacent parti- 

 cles will be 1000000000000 ^^ °^ ^ §"■• ' ^"^ ^y P^°P- ^' *^^ cohesive 

 force of the whole cylinder will be one grain. Let now an equal 

 cylinder be formed of the same matter, the particles having each 



a diameter = ,000000000000 ^^ °^ ^" '"'^^^ 5 the weight of each 



particle will be = t ^th of a grain, the cohesion be- 



^ {1 000000000000 }3 "= 



tween two adjacent particles will be loooooooooooooooooo ^^ °^^ §'>•- 



and the cohesion of the whole mass will be 1000000 grains = 

 ISOlbs. or about 1-i-th hundred weight ; and if the particles were 



reduced to th part of what they were last supposed, the 



force of cohesion of this cylinder, whose diameter is one inch, 

 would be increased 1000000 times. Whence it is manifest that 

 in a mass of matter, the cohesive force may be very great, 

 though the attraction of such a mass is absolutely insensible, the 

 force bemg inversely as the square of the distance. This subject 

 may be experimentally illustrated : Let chalk, calcined bones, 

 white lead, or any other insoluble matter be reduced to a coarse 

 powder, moisten this with water, and let it be dried with a very 

 moderate degree of heat ; when dry, it will form a mass, of 

 which the parts cohere with very little force, the cohesion scarcely, 

 if at all, exceeding their weight. Let it now be reduced to an 

 impalpable powder, and treat it similarly, when it will be found 

 that the cohesive force will be very great, the mass, when sus- 

 pended by one of its parts, being able not only to sustain its own 

 weight, but also a very considerable additional one. Since these 



