368 On the non conducting potver of Water. 



not more embarrassing to the lungs, than the action of the 

 blast and falling water, behind this amazing cataract. 

 I remain most sincerely your obedient servant, 



Basil Hall* 



Art. XV. — On the non conducting 1 power of water in rela- 

 tion to heat; by W. M. Mather. 



Water has by some been considered as a conductor, by 

 others a non-conductor of heat downwards. Count Rum- 

 ford, seems to have been the first who developed the manner, 

 in which fluids receive an increase of temperature. He ob- 

 served during the cooling of water in a glass vessel, two cur- 

 rents running in opposite directions. The exterior one was 

 directed from the upper to the lower part of the vessel — the 

 other passing through the centre from the bottom to the sur- 

 face of the fluid. The reason of this is perfectly evident ; 

 the particles of the fluid adjacent to the surface of the vessel, 

 give up a portion of their free caloric, and become specific- 

 ally heavier than the neighboring ones, in consequence of 

 which, they sink to the bottom, displacing others that are 

 warmer, which rise to the surface, give out a portion of their 

 caloric and sink in their turn to give place to others. This 

 motion of the particles continues, until the fluid acquires the 

 same temperature as the surrounding bodies. The Count 

 conceived that if the motion of the particles could be pre- 

 vented, the fluid would not receive an increase of tempera- 

 ture. He rendered this highly probable ; for by introducing 

 into water, substances not chemically soluble in it, it was 

 found that the tendency to receive an increase of tempera- 

 ture (when exposed to heat) was diminished in proportion, as 

 the motion of the particles was retarded. From this he in- 

 ferred, that water could not conduct heat, except by the mo- 

 tion of its particles. Dr. Murray's experiment to shew that 

 water is a conductor of heat downwards, seems at the first 

 glance to be conclusive. 



The following account of it is given in Websters Manual 

 of Chemistry. " If we carefully pour hot oil upon water, in 

 a tall glass jar w T ith delicate thermometers placed at different 

 distances under the surface, it will be found that those near 

 the heated surface indicate increase of temperature ; it might 

 here be said, that the heat was conducted by the sides of the 

 jar, and so communicated to the water ; to obviate such ob- 



