228 GREATEST DE^'SITY OF 'VVAtER. 



thrown on the barrel : the pyrometer gave Ql" : tlie chalk was 

 in a firm state of limestone. 



No. 11. — with 4 cwt. The barrel stood without any erup- 

 tion or exudation, till the heat rose to 25°. There was a loss 

 of 3.6 per cent.: the lesult was superior, in hardness and 

 transparency, to the lastj having somewhat of a saline 

 fracture. 



No. 12. — with 5 cwt. The result, with a loss of 2.4 yer 

 cent., was of a quality superior to any of those lately obtained. 

 Dertuctions of These experiments appear to answer the end proposed, of 

 the pressures ascertaining the least pressure, and lowest heat, in which lime- 

 limestone, mar- stone can be formed. The results, with various barrels of 



ble, and fused (jjffeient sizes, agree tolerably, and tend to confirm each other. 



carbonate ex- ° •' 



pressed in at- The table shews, when we compare numbers 1,2, 8, 10, II, 



mospheresand J2 r^\^^^ ^ pressure of 52 atmospheres, or 1/00 feet of sea, 



ui depths of the ' ... 



sea. is capable of forming a limestone in a, proper heat. That 



under 86" atmospheres, answering nearly to 3000 feet, or about 



half a mile, a complete marble may be formed : and lastly. 



that with a pressure of 173 atmospheres, or 5700 feet, that is, 



little more than one mile of sea, the carbonate of lime is 



made to undergo complete fusion, and lo act powerfully on 



other earths. 



(To he coniinned.) 



V. 



Jtnvestigation of the Temperature at •which Water is of greatest 

 Density ; from the Experiments of Dr. Hope, on the Con- 

 traction of Water by Heat at low Temperatures. By J, 

 Dalton. 



{Concludedfrom vol. iii. p. 380.) 



To Mr. NICHOLSON. 

 SIR, 



JLN my last letter I apprehend it has been shewn that the 

 iio^^^'T ^J.pnv'i- results of Dr. Hope's first experiment demonstrate that water 

 meiirs. is densest at or near the 360°. I now proceed to shew that 



the remaining five experiments, as far as they apply, tend to 



establish the same conclusion. 



Tlie 



Farther consi 

 dprati'w of Dr 



