328 On the Construction of Kitchen 



this washing out in boiling must be greatly facilitated 

 and expedited by the continual and rapid motion into 

 which the contents of a boiler are necessarily thrown 

 when heat is applied to one side of it only, especially 

 when that heat is sufficiently intense to keep the liquid 

 continually boiling with vehemence. I ought, no doubt, 

 to have foreseen this ; but how difficult is it to foresee 

 any thing ! It is much easier to explain than to predict. 



If it be admitted that fluids in receiving and giving 

 off heat are necessarily thrown into internal motions 

 in consequence of the changes of specific gravity in 

 the particles of the fluid, occasioned by the alteration 

 of their temperatures, we shall be able to account, in a 

 manner perfectly satisfactory, not only for the appear- 

 ances observed in' the experiments above mentioned, 

 and for the superior richness of the soup made by the 

 Bavarian cook in her boiler, but also for several other 

 curious facts. 



When the copper stewpan, containing cold water 

 and a piece of meat, was put into an iron oven, heated 

 by a fire situated below it, as the bottom of the oven on 

 which the stewpan was placed was very hot, the heat, 

 passing rapidly through the flat bottom of this metallic 

 utensil, communicated heat to the lower stratum of the 

 water, which, becoming specifically lighter on being 

 thus heated, was crowded out of its place, and forced 

 upwards by the superincumbent colder and conse- 

 quently heavier liquid. This necessarily occasioned 

 a motion in every part of the fluid, and this motion 

 must have been rapid in proportion as the communica- 

 tion of heat was rapid ; and it is evident that it could 

 never cease, unless all the water in the stewpan could 

 have acquired and preserved an equal and a permanent 



