rOL. XLVI.] PHILOSOPHICAL TRANSACTIONS. 01 7 



thermometer first Introduced into use in England, by the same excellent philo- 

 sopher, has been so little improved for more than half a century, that it serves 

 for little more than amusement. 



For some years past, several eminent philosophers have applied themselves to 

 bring this instrument to better condition, and to render it more useful ; and 

 among them the great Sir Isaac Newton did not think it unworthy his attention. 



It seems now to be pretty generally agreed, that thermometers made with 

 quicksilver are preferable to all others ; that extravagant fluid, as Mr. Boyle calls 

 it, being most easily susceptible both of heat and cold, and, when well purified, 

 not liable to be obstructed in its motion. 



Dr. M. had, by some years experience, found both the excellence of them, 

 and the necessity of keeping them in the open shaded air, before he met with 

 the learned and curious essays medical and philosophical of Dr. George Martina, 

 in which he so much recommends their use; and it was no small satisfaction to 

 find that gentleman had proved, by experiments, that quicksilver both heats and 

 cools faster than any liquor we know ; faster, I am sure, says he, than water, 

 oil, or even spirit of wine, and never freezes, by any degree of cold hitherto 

 observed. 



There is another particular of great importance, which probably we may rather 

 wish than hope to see made a general practice, recommended by the same gen- 

 tleman ; viz. the constructing all thermometers with one scale. But if this may 

 not be expected, certainly no thermometer should be made without adjusting two 

 determinate and sufficiently distant points of heat and cold ; such, for instance, 

 as those of boiling water, and of water just beginning to freeze, and the inter- 

 vening space divided into a convenient number of equal degrees. By this 

 means we should be able to know what is meant by any specified degrees of heat 

 or cold, and a comparison might be easily made of the state of the air in distant 

 places, provided the instruments were accurately made. 



On Monday Nov. 21st, 1748, in the evening, the sky very clear, the wind 

 N. and a smart frost, the barometer was 30 inches -^. At near g^ the thermo- 

 meter without the window at 7° below 0, or freezing point. The thermometer 

 within, of the same construction with it, and not a yard from it, (the room hav- 

 ing had no fire in it this season) at 5° nearly above O. 



On Tuesday morning, at 4*" 20"*, the barometer was at 30 -^ inch ; the 

 thermometer without at 1 4*^-1- below 0; that within at 2% above 0: which waS; 

 surprising. At 7*' 40"" the same morning, the sky looked red and lowering i 

 and the barometer was fallen to 30t-|-5^, the thermometer without risen to 5° 

 below freezing point, but that within fallen to 1° above; the wind getting about 

 to w. and s.w. and before 10 in the morning there was some rain, and this se- 

 vere frost went oft". At this last-mentioned hour the thermometer without hac} 



VOL. IX. 4 K 



