84 Inquiry concerning the Natiire of Heat, 



spread itself out on the floor of the room ; and the per- 

 forated circular sheet of paper, which was laid down 

 horizontally on the platter, effectually prevented any of 

 the air so cooled from being thrown upwards against 

 the bottom of the conical vessel (placed immediately 

 over the platter), by any occasional undulation of the air 

 in the room. 



To preserve the air of the room in a state of perfect 

 quietness, not only the doors and windows, but even 

 the window-shutters of the room were kept shut ; so 

 much light only being admitted occasionally as was 

 necessary to observe the thermometers which were 

 placed in the conical vessels. 



In order to guard still more effectually the bottoms 

 of the vessels which were cooling from the effects of 

 occasional undulations in the air of the room, over each 

 of these vessels there was drawn a cylindrical covering 

 of very fine thin post paper, the lower open end of 

 which projected just half an inch below the horizontal 

 level of the flat bottom of the vessel. These cylin- 

 drical coverings of post paper were made to fit as ex- 

 actly as possible the cylinders of pasteboard by which 

 the sides of the conical vessels were covered and de- 

 fended from the air ; and the warm coverings of fur 

 (rabbit-skins) were put over all. 



To confine the heat still more effectually, a quantity 

 of eider-down had been introduced between the outside 

 of each conical vessel and its cylindrical neck, and the 

 inside of the hollow cylinder of pasteboard in the axis 

 of which it was fixed and confined. 



The result of this experiment was very conclusive. 

 The conical vessel which was suspended over the ice- 

 cold pewter platter cooled through the standard interval 



