43 On the Boiling Point of Mercury, &g, 



tcntion paid to this branch bt" commerce as in our republic, 

 which is of so much the greater consequence to our state, 

 as the necessary expenses ot stores and iitthig for the whale- 

 fishery are ahnost all defrayed from the profits of it. As 

 long as these wise ordinances and regulations are punctu- 

 ally observed, and no breach of them allowed, notwith- 

 standing the high wages, which may be considered as one 

 cause of its dechne, it may still flourish. 



VII. On the Boiling Point of Mcrnmj, and the Fixing 

 Points of Lead and Tin, By Mr. James Crichton, 

 of Glasgow*. 



To Mr. Tilloch. 



JL HAVE to request that you will correct a small error in the 

 account of my thermometer, inserted in number LVIII, 

 (p. 147). The bar is composed not of iron and zinc, as 

 printed by mistake, but of steel and zinc. The engraver 

 has also made the scale to read from right to left, instead of 

 the contrary ; but this is not material. 



I have it now in my power to send you the results of a 

 number of interesting experiments respecting the boiling 

 point of mercury, and the fixing points of lead and tin, which 

 I think may answer some important purposes to the philo- 

 sophical world. A detail of all the steps followed, which 

 were similar to those stated in my last communication, 

 would only take up time unnecessarily. 



The steady uniform point at which block-tin fixes sur- 

 passes my expectations, and is far more determinate than 

 that of water. Lead has not, like tin, the property of in- 

 stantly depressing and as instantaneously raising the ther- 

 mometer at the moment of congelation. 



Having had occasion, in constructing some very high- 

 ranged thermometers, to take for the purpose of graduation 

 some point much higher than that of boiling water, as in 

 prolonging a scale to 500 or 600" from so comparatively 

 contracted a scale, errors must unavoidably be introduced, 

 I had recourse to the writings of the most respected British 

 and foreign chemists, to find from them the fixing points 

 of lead and tin. In this search. I was greatly disappointed, 

 tor they do not agree amongst themselves, varying so much 

 as 30, 40, sometimes 70 degrees. Besides, having good 

 jeasou to suspect 'that none of them were near the truth, I 



* Communicated by the Author. 



resolved 



