CiiAP. II.] Chemical Philosophij. 1 .3 1 



invented and adopted*. Tlir Thcnnomcfcr, wliicli 

 had been first used about the l)egliniing of the 

 preceding century, was constructed on a new aiul 

 improved plan, by sir Isaac Newton, in I70I. Me 

 chose, as fixed pohits of graduation, those at which 

 water freezes and boils; a clioice which the expe- 

 riments of succeeding philosophers have proved to 

 be the most wise and convenient. He also iutro- 

 duced the use of oil to fill the tube, instead of 

 alcohol, under an idea that the former was liable 

 to fewer disadvantages than the latter. 13iit, after 

 all the labours of sir Isaac, this important instru- 

 ment was imperfect, and could by no means be 

 considered as an exact standard for pointing out 

 the various degrees of temperature. Accordingly, 

 about the year 1724, Mr, Fahrenheit, of Amster- 

 dam, suggested the use of thermometers made \\ ith 

 mercurijy and presented one of this kind to the 

 Royal Society of London. It was soon found tiiat 

 this fluid was preferable to all others, being more 

 homogeneous, more easilj" freed from air, more 

 regularly expansible by diflerent degrees of heat, 

 and more difficult to congeal. Mr. Fahrenheit 

 also proposed a new mode of graduating the in- 

 strument. His thermometer has since come into 

 general use in Great Britain, America, and in tlut 

 various parts of the world in which British habits 

 prevail. 



In 1750 M. Reaumur, a French philosoi^Iicr, 

 constructed a thermometer on a new plan. He 

 adopted a mode of graduation diflerent both from 

 Kewton and Fahrenheit, and resumed the u:>e ol 



^- See Additional Notes — (W). 

 K2 



