concerning Heat. 145 



tween the bottom and top, and were soldered fast in 

 them. 



Each of the vessels was made flat on the side where 

 the copper cylinder was fastened, so that the extremity 

 of the cylinder did not project into the vessel, but was 

 level with the flattened part. 



This instrument was supported at the height of eight 

 inches and a half above the table on which it stood, by 

 means of three feet, two fixed to one of the vessels, 

 and one to the other. 



One of these vessels being filled with boiling water, 

 the other with water at the freezing point, as the two 

 extremities of the cylinder were placed in immediate 

 contact with these two masses of fluid, a change of 

 temperature must necessarily take place by degrees in 

 all the interior parts of the cylinder. For the pur- 

 pose of observing this change, three vertical holes were 

 made in the cylinder, into which were introduced the 

 bulbs of three small mercurial thermometers. One 

 of the holes was in the middle of the cylinder, the 

 others midway between the centre and either extrem- 

 ity. 



Each of these holes is four lines in diameter, and 

 eleven lines and a half deep ; so that the bulbs of the 

 thermometers, which are three lines in diameter, were 

 all in the axis of the cylinder. 



When the thermometers were put in their places, the 

 holes were filled with mercury, in order to facilitate the 

 communication of heat from the metal to the bulb of 

 the thermometer. 



To keep the hot water constantly boiling, a spirit- 

 lamp was placed beneath the vessel containing it; and 

 to keep the cold water constantly at the temperature of 



