xix Pyrometer or Thermometer 245 



strongest that vessels of clay can support." A few 

 months after his paper had been read at the Eoyal 

 Society, Mr. William Playfair, an Edinburgh Professor, 

 wrote to Mr. Wedgwood the following letter (London, 

 12th September 1782) : " Sir I had the pleasure of 

 being present at the reading of your very ingenious 

 paper on your newly-invented Thermometer before the 

 Eoyal Society last spring, and of joining in the general 

 satisfaction that such an acquisition to Art gave all 

 present. I have never conversed with anybody on the 

 subject who did not admire your Thermometer, and 

 considered it as being as perfect as the nature of things 

 will admit of for great heat; but I have joined with 

 several in wishing that the scale of your Thermometer 

 were compared with that of Fahrenheit's (so universally 

 used for small degrees of heat), that without learning a 

 new signification, or affixing a new idea, to the term 

 Degree of Heat, we might avail ourselves of your useful 

 invention. The method proposed in the enclosed paper 

 occurred to me as one applicable to this purpose, and I 

 lay it before you with all deference to your better 

 judgment of the subject. I should be glad to know 

 where I could purchase some of your Thermometers, 

 as I can get none here in town. I am, sir, with 

 much regard, your most humble servant, WILLIAM 

 PLAYFAIR." 



Wedgwood followed Mr. Playfair's advice. In his 

 next papers, sent to the Eoyal Society, he gave a re- 

 duction of the degrees of his Thermometer to Fahren- 



