340 Mr. Herapathonthe Causes, Laws, and principal [May, 



paper, two inches square, proved inadequate to discharge my 

 galvanic apparatus of coils, yet at a distance 70 times greater, 

 a strip of the same paper, one- third of an inch wide, and 20 

 inches long, caused an instantaneous discharge of the electrical 

 battery. 



Article III. 



A Mathematical Liquin/ iuto the Causes, Laws, and principal 

 Fhccnomena of Heat, Gases, Gravitation, Sfc. By John He- 

 rapath, Esq. (In a Letter to D.Gilbert, Esq. MP. VPRS. 8cc.) 



{Continued from p. 293.) 



Of the Laws of Gaseous Bodies. 



Dejinitions. 



Def. 1. — The homogeneity of a gas is the perfect equality of its 

 atoms, or particles, throughout, in quantity of matter, it is of 

 no consequence whether the atoms are similar in figure or not ; 

 their figures might be very different, provided, however, the 

 quantity of solid matter in each is the same. 



Def. 2. — Density is the quantity of matter in a given space, 

 when the atoms, or particles, whatever be their relative magni- 

 tudes, are uniformly disposed in the medium. 



Cor. 1 . — The mean density of any body is, therefore, propor- 

 tional to the whole quantity of matter, divided by the whole bulk, 

 or magnitude of the body. 



Cor. 2. — In a homogeneous body, the density is equal to the 

 laass of an atom drawn into the number contained in a given 

 space. 



Def. 3. — Numeratom is a term I have employed to express 

 the number of atoms, or particles, distributed throughout a given 

 space, without respect to the density or homogeneity of the 

 body. 



Cor. — Hence the numeratom of a homogeneous body is pro- 

 portional to the density directly, and the mass of a particle, or 

 atom, inversely. 



This conclusion might also have been drawn from Cor. 2 of 

 the pieceding definition. 



Def. 4. — The elasticity of a gas is the force with which it 

 endeavours to expand itself, or with which it resists compres- 

 sion ; and is estimated by the amount of its action against 

 similar and equal portions of the containing bodies. 



General Considerations on Force and the Constitu- 

 tion OF Gaseous Bodies. 



Force is the cause of any change, or is that power, by which 

 the change is produced. If, therefore, a body be perfectly free 



