IS 



01' Till: PROPERTIES OF MATTER. 



LEOT. 

 II. 



sum of me- 

 tals. 



All bodies are some way or other affected by heat ; 

 and all metallic bodies are expanded in length, breadth, 

 The expn- arid thickness thereby. The proportion of the expan- 

 sion of several metals, according to the best experiments 

 I have been able to make with my pyrometer, is nearly 

 thus : Iron and steel as 3, copper 4 and a half, brass 

 5, tin 6, lead 7. An iron rod 3 feet long is about one 

 70th part of an inch longer in summer than in winter. 



The pyrometer here mentioned being (for aught I 

 know) of a new construction, a description of it may 

 perhaps be agreeable to the reader. 



The pyro- 

 meter 



A~\ 



O 



A. 



A A is a flat piece of mahogany, in which are fixed 



If the particles of which the body is actually formed, be constructed 

 in the same manner; then the vacuity will become three-fourths of the 

 space occupied by the body. Carrying the supposition still further, 

 \ve may suppose the last mentioned particles constructed in the same 

 manner, the vacuity will then be seven-eighths ; and if the series be 

 carried forward to the tenth order of particles, the vacuity will ex- 

 ceed the matter one thousand and twenty-three times. A very ob- 

 vious illustration of the effects of caloric in producing porosity is shewn 

 in the formation of vesicular vapour or steam, which may be increas- 

 ed to many thousand times its original bulk, by an increase of tem- 

 perature. 



