in Fluids. 255 



ity of the passage of the Heat by the times elapsed in 

 heating and cooling the thermometer through the whole 

 length of its scale, or between the point of freezing to that 

 of boiling water, I have taken the times elapsed in heat- 

 ing and cooling it 80 degrees in the middle of the scale, viz. 

 between 80 and 160, as the measure of the conducting 

 powers of the substances through which the Heat was 

 made to pass. 



I have, however, noted the times which elapsed in 

 heating and cooling the instrument through a much 

 larger interval, namely, through an interval of 168 de- 

 grees in heating, or from 32 to 200, and in cooling 

 through 1 60 degrees, or from 200 to 40. 



In respect to the cooling of the instrument, it is neces- 

 sary that I should inform my reader, that, though I have 

 not in the tables of the experiments mentioned any 

 higher temperature than that of 200, yet the instrument 

 was always heated to the point of boiling water, which, 

 under the pressure of the atmosphere at Munich, where 

 the experiments were made, was commonly about 209-3- 

 deg. of Fahrenheit's scale. The instrument, being kept 

 in boiling water till its thermometer appeared to be quite 

 stationary, was then taken out of the water and instantly 

 plunged into melting ice, and the time was observed and 

 carefully noted down when the liquid in its thermometer 

 passed the division of its scale which indicated 200, as 

 also when it arrived at the other divisions indicated in 

 the tables. 



With regard to the four last-mentioned experiments 

 (No. 2, 4, 6, and 8), it will be found, on examination, 

 that their results correspond very exactly with those be- 

 fore described ; and they certainly prove in a very deci- 

 sive manner this important fact, that a small proportion 



