ill Kev. J. B. Einmell on Solids and Liquids. 



are n spheres on each edge, the number in the whole solid is 



M^ ; therefore the whole solidity of the spheres is ^'' ; and 



the sum of the interstices = — ^!,"-^^ ^-^ ; which is known 



K- 



when a is given. 



The whole content of a cube, whose side is A = A'; 

 therefore when the particles are arranged in a square form, 



the sum of the interstices = A* — '-^-^ . The anjrle a in 



6 *= 



this paper, is the angle B in the former papers here quoted. 



In any solid, let a become a right angle just before it fuses; 



its content is A^; after fusion, let the distance A become 



A + /i; the content then is ^^ — - ~ = i — --^ x — ; 



hence, in order that there be neither expansion nor contrac- 

 tion during fusion, h = A > "V -, 1 I ; if /^ be greater, the 



body expands during fusion ; if less, it contracts. And the ut- 

 most expansion of which a solid is susceptible = A^ •; 1 > 



= — ; this comprehends the whole possible range from the 



true zero, or total privation of heat, and results from the change 

 which may take })lace in the relative position of equal sphe- 

 rical particles, held together and in perfect contact, by co- 

 hesion. 



The particles of liquids are i?i equilibrio between two op- 

 posite forces, viz. attraction and the repulsive force of caloric. 

 The latter, in liquids decreases more rapidly than the former; 

 for liquids expand by heat, and contract by being cooled : 

 but if it varied inversely as a lower power of the distance than 

 the centripetal force, the contrary must happen ; if according to 

 the same power, matter could not exist in a liquid form, except 

 under pressure. This is evident from the nature of forces. 



Now, when a solid is heated, the angle a increases, until 

 the force of cohesion is overcome; the particles then separate 

 from each other, and are arranged in regular hexagons : by 

 the evidence derived from experiment, the foi'ce of repulsion 

 exceeds that of attraction to a certain distance, beyond which 

 it is inferior to it ; the distance of the point of equilibrium is, 

 therefore, a measure of the distance between the particles ; and 

 this }ioint recedes from the particles as the temperature is in- 

 creased; until, by a certain increase of temperature, the par- 

 ticles become altogether repulsive, or the matter becomes 

 gaseous. J. B. Emmett. 



Great Oiihebiirn, March \2, 1827. 



Lxxxn. (hi 



