xix Pyrometer or Thermometer 247 



to Wedgwood, announcing that he had been elected a 

 Fellow of the Eoyal Society on the 16th of January 

 1783. In a later letter Sir Joseph requested Wedgwood 

 to select some person skilled in the mystery of potteries, 

 to accompany Lord Macartney to the Emperor of 

 China, to acquaint himself with any mode of manu- 

 facture used by the Chinese, and of which the artists 

 of this country were as yet ignorant. " To you, sir," 

 he added, "who have always practised Pottery as a 

 Science instead of an Art, we naturally look up for 

 advice where to meet with such a person." 



Sir Joseph's letter of the 6th of April 1784 relates 

 to Wedgwood's Thermometer, and other affairs : " Dear 

 Sir Your paper proposing a mode of connecting the 

 scale of your Thermometer with Fahrenheit's I have 

 received and read with care. The whole meets with 

 my entire approbation, and I shall take the first oppor- 

 tunity in my power to read it to the Eoyal Society. 

 One thing, however, I must remark, which is, that you 

 seem not to hare heard of the experiments made last 

 winter at Hudson's Bay, by which the point at which 

 mercury congeals into a malleable metal is fixed to be 

 40 below zero on Fahrenheit's Thermometer. All 

 points of cold, therefore, below that which have been 

 observed by a mercurial Thermometer must be set aside. 

 It is a matter of no consequence to you, only will cause 

 a trifling alteration in the notes on the scale of your 

 Thermometer. 



" You are, believe me, good sir, much wanted here. 



