iji Fluids. 257 



ever) in small masses, or which has a very large surface 

 in proportion to its solidity. 



In the foregoing experiments with stewed apples^ the 

 passage of the Heat in the water (which constituted by 

 far the greatest part of the mass) was doubtless ob- 

 structed in both these ways. The mucilaginous parts of 

 the apples diminished very much the fluidity of the wa- 

 ter, at the same time that the fibrous parts served to em- 

 barrass its internal motions. 



In order to discover the comparative effects of these two 

 causes, it was necessary to separate them, or to contrive 

 experiments in which only one of them should be per- 

 mitted to act at the same time. This I endeavoured to 

 do in the following manner. 



To ascertain the efl^ects produced by diminishing the 

 fluidity of water, I mixed with it a small quantity of 

 starch, namely, 192 grains in weight to 2276 grains of 

 water ; and to determine the effects produced by merely 

 embarrassing the water in its motions, I mixed with it 

 an equal proportion (by weight) of eider-down. The 

 starch was boiled with the water with which it was mixed, 

 as was also the eider-down. This last-mentioned sub- 

 stance was boiled in the water in order to free it from air, 

 which, as is well known, adheres to it with great obsti- 

 nacy. 



In order that these experiments may with greater 

 facility be compared with those which were made with 

 stewed apples and with pure water, I shall place their re- 

 sults all together in the following tables. 



