[ jcS ] [Book II. 



CHAP. III. 



OF .EXPANSION. 



Experiments proving the exfanjlfje Force of Fire, or Caloric, //////- 

 Mints for meafuring Degrees of Heat. Thermometers. ~ Dr. Black's 

 Made of meafuring high Degrees of Heat. Mr. Wedgwood's. 



CALORIC, as was intimated in the preceding 

 chapter, expands all bodies which it penetrates, 

 more or lefs, in proportion to its quantity, and to 

 the nature of thofe bodies. The expanfion of water, 

 even previous to its afiumingthe form of vapour, may 

 be feen in an eafy experiment. If a quantity of cold 

 water, contained in a clear flafk, is immerfed in a 

 veflel of boiling water ; as the heat enters, the water 

 in the flufk will be feen to rife in the neck tiil it 

 overflows. 



An iron rod a foot long being heated red hot, be- 

 came ^ -th longer than before; and a glafs cylinder, a 

 fathom long, under the fame cireumftances, gained 

 v ',.th in length. A metalline ring thus heated was in- 

 creafed T-|-^ in its diameter : and a glafs globe became 

 extended T A- - part by the heat of the hand only ap- 

 plied to its furface *. 



It is a well-known practice to immerfe razors, or 

 any inftruments which are required to cut fmooth, in 

 warm water j as the whole of the metal expands, the 

 edge is alfo proportionably expanded, and confequently 

 is rendered fo much finer and fmoother. 



An inftrument was invented by Mr. Jones, for mea- 

 furing the force of expanfion, which by the flame of a 



* Boerhaave's Chem. by Shaw, Vol. I. p. 299. 



farthing 



