OREA,TEST J>EXSITy OF WATEK. IS^ 



fop in temperature, and to have gained 8°, whilst ihe top has 

 rapidly passed from 33" to 48", an increase of 15". — If we 

 Jake 40" for the point of greatest density, the bottom never 

 attains it during the whole experiment, whilst the middle and 

 lop gradually arrive at, and surpass h long before the eon- 

 elusion. 



The sixth experiment will now be easily explained. A fkig- Dr. Iioi>e'3 

 orific mixture was- put into the vessel surrounding the middle ^gj^^^^^j"" 

 «f the tall jar, which contained water of 392''. The theriaQ- a cooiifig zone, 

 iRL'tci was observed as und«r ; 





Bottoni. 





Top. 



At commencement. 



— 39 . 5 



— 



^9^5 



in 10 minutes, 



- 39 4- 



— 



38 -f 



25 



— 39 + 



— 



36,5 



35 



— 39 



— 



36— 



55 r 



— 39 



— 



35 



1 h in 



— 39 — 



— 



34 + 





: 35 



— 39 — 



— 



34 — 







~ 39 — 



—*. 



33 + 



Here the first obsen,'ation is sufficient of itself to decide by Reasons ftw 

 which theory the whole are to be explained. In 10 minutes ^^^^^^^^^5^^^^^ 

 x\c observed a fall of nearly half a degree at the bottoia, and greatest denaty 

 one of l|" at top. How will Dr. Hope account for the 

 descent of the bottom thermometer ? Water of 36" or 37** 

 cannot descend into water of 39.5, that of less density into 

 greater ; it must then be the effect of the propagation of cold 

 downwards by the proper conducting power of the liquid. 

 Granted : but if this was the case, a thermometer m the centre 

 of the jar, should have indicated 32o; and orae in the middle, 

 between the centre and the bottom o()°, or ther-eabouts ; for 

 every one allows, that in the proportion of heat (or cold) along 

 any solid body, the effect is produced gradatim. This conclu- 

 sion, Itowever, would ill accord with what was observed in the 

 third experiment. Let us now try this experiment by the other 

 point, ov- 36". — The sudden cold applied to the middle of the 

 jiar would quickly reduce the contiguous liquid to 36", and 

 below ; this gives it a force of descent by Which the tempera- 

 ture 



