60 



REPORT ]875. 



from api^reciably good conductivity of -water itself may be inferred with 

 some degree of probability from the observations of Prof. Guthrie*, that 

 films of water offer from four to fifteen times less resistance to the passage of 

 heat through them than those of any other liquid (mercury excepted) of 

 whose relative thermal resistances he obtained determinations. Prom Dr. 

 Sterry Hunt's recent publication f the following Table of porosities and 

 densities of various rocks is extracted, showing to what extent the presence 

 of water among such strata may be expected, according to the general 

 conclusions, to affect their thermal conductivities and to diminish their 

 resistances. 



* Philosophical Transactions of the Royal Society, 1869, part 1, p. 659 (Table). 



t Chemical and Geological Essays, by Prof. T. Sterry Hunt, p. 166 (1875). This is 

 reprmted from the Report of the Geological Survey of Canada for 1863-66, pp. 281-283. 

 By an oversight in this Table the Caen limestone is described as Tertiary by Dr. Sterry 

 Hunt instead of Secondary. 



