244 ' Josiah Wedgwood CHAP. 



Muschenbrock, Desaguliers, Ellicot, and Smeaton 

 the engineer, made experiments with the pyrometer, 

 but they never reached so intense a degree of heat as 

 that attained by Wedgwood. The advantages of an 

 accurate measure of the heats of metals, furnaces, and 

 other objects, are obvious to every one concerned in 

 operations by fire, and Wedgwood's invention for 

 supplying this grand desideratum was as simple as it 

 was ingenious. 



All clays are contracted, or have their bulk dimin- 

 ished, by fire, more and more in proportion to the 

 intensity of the heat ; e.g. little masses of the same clay 

 are adjusted to enter the wider end of a graduated 

 canal ; so that, after passing through fire they will 

 go further into the canal, the point at which they 

 stop showing their quantity of diminution. This 

 point is numbered, and exhibits the heat which the 

 clay has undergone. This instrument Wedgwood first 

 called a Pyrometer, or heat-measurer ; but that name 

 having previously been appropriated to a machine 

 of a different kind, for measuring the expansion of 

 bodies, he thought it better to retain the name of 

 " Thermometer." l 



Wedgwood sent his first paper to the Eoyal Society 

 on the 9th of May 1782. His paper was entitled, " An 

 attempt to make a Thermometer for measuring the 

 higher degrees of Heat, from a red heat up to the 



1 Wedgwood explained his views to the Royal Society (Philosophical 

 Transactions, vol. Ixxii., and afterwards in vols. Ixxiv. and Ixxvi.). 



