278 Inquiries concerning the Mode of the 



several interesting phenomena of nature, which before 

 were enveloped in much obscurity. 



When a hot solid body is plunged in a cold liquid, 

 there can be no doubt concerning the existence of the 

 vertical ascending currents which are formed in the 

 liquid, and which convey to the surface the heat which 

 its particles have received ; but with respect to the strata 

 of liquid situated under the hot body, are they or are they 

 not heated by this body by means of a direct communication of 

 heat from above downwards^ from f article to particle,, these 

 particles remaining in their places? This is a question on 

 which philosophers are not yet agreed. As it is a ques- 

 tion of great importance, I have long meditated on the 

 means of deciding it ; and after several unsuccessful 

 attempts, I have at last succeeded in making an experi- 

 ment which I think is decisive. 



As the apparatus which I used for this experiment, 

 and which I have the honour of laying before the assem- 

 bly, is somewhat complicated ; and as it is indispensably 

 necessary to be intimately acquainted with it, in order to 

 form a judgment concerning the degree of confidence 

 which the results of the experiment may deserve, it is 

 necessary to give a detailed description of this machinery. 

 The annexed figure gives a distinct representation of its 

 principal parts. It is drawn on a scale of a quarter of 

 an inch to the inch, English measure. 



A B (Plate VII.) is a board, of oak, seen in profile; 

 it is ii inches thick, 18 inches long, and n inches 

 in breadth. It serves to support two square upright 

 pillars, C C, i8J inches in height and i| inches square. 

 They are firmly fixed in the board at the distance of 1 1 

 inches asunder, and serve to support the two cross- 

 pieces, D E, F G, at different heights. 



