Jg0 MAXIMUM .DENSITY Or WATER, 



VII. 



RetnarLs on a Letter of Mr, f) alt on, concerning the Maximum 

 Dcnfihj of Water ; vdlh an Account of two Experiments of Dr K . 

 Hope, tending to Jhevj that it takes place at a Temperature 

 above the freezing Point. In a Letter from T. I. B, 



To Mr. NICHOLSON. 

 SIR, 



Mr ft Dalto.fs ^ N N °' ^ ° f y ° Ur J ourna1 ' P a S e 28 » Mr * Da,t ° n haS P ub " 

 letter. liflied forae remarks upon Count Rum ford's experiments, re- 



lating to the maximum denfity of water, where he explains 

 the riling of the thermometer in the cup, by obferving that 

 it acquired heat by the proper conducting power of water. 

 This, I fhould think, is by no means probable ; for the con- 

 dueling power of water is not futiicient to produce fuch a rapid 

 effea. 



The circumftances of the two thermometers by the fide o 

 the i ball and cup, in the Count's two firft experiments, I 

 think are perfectly confident with his principle: the cup, 

 very probably, did overflow, which might have been afcer- 

 tained by a thermometer placed below. 



In the conclufion of this letter Mr. Dalton exprefles a wifli 

 that Count R. or fome one in pofleffion of a fimilar apparatus, 

 would repeat the Count's firft experiment, with this difference, 

 that the mafs of water mould be at 40° and the ball at 32°, 

 in which cafe, he fays, the thermometer would not be at all 

 affected on the Count's principle; neither would it be affected 

 (on Mr. D.'s principle) if the tenacity of the water counter- 

 acts the force of defcent : and what conclufion could be drawn 

 from fuch a variation of the experiment ? 

 Experiments of The following experiment was made by Dr. Hope, pro- 

 Dr. Hope. feflbr of chemiftry in Edinburgh, to afcertain the point at 



which water has the greateft denfity, — and it appears to me 

 lo be perfectly decifive. 



He filled a jar with ice-cold water, and expofed it to the 

 air of a room at 52° : he fufpended in it two very delicate 

 thermometers, one at half an inch from the bottom, and the 

 other at the fame diflance from the furface of the water : the 

 thermometer neareft the bottom was firft affected, and con- 

 - a 5 tinuetf 



