ON HEAT AND LIGHT. 155 



Having procured two cylindrical veflels of tin, each fixDefcnption of 



inches in diameter and fix inches high, I fattened them toge- ij?^ gyfindridl 



(her by means of a folid cylinder of copper fix inches long and tin veflels were 



an inch and half in diameter, which was fixed horizontally be- "nnefted by a 



' / bar of copper. 



tween the two tin veflels. The extremities of the cylinder 



pafied through two holes an inch and half in diameter, made 



for the purpofe in the fides of the veffels, midway between the 



bottom and top, and were foldered faft in them. ,.^, , 



JEach of the veffels was made flat on the fide where the cop- 

 per cylinder was fattened, fo that the extremity of the cylinder 

 did not project into the veflel, but was level with the flattened 

 part. 



This infirament wa,s fupported at the height of eight inches 

 and half above the table on which it flood, by means of three 

 het, two fixed to one of the veflels, and one to the other. 



One of thefe veflels being filled with boiling water, the pther The veflels -filled 

 with water at the freezing point; as the two extremities of the with w o ater > onj 

 cylinder were placed in immediate contacl with thefe two ot h er at'32 . 

 mafles of fluid, a change of temperature mutt neceflarily take 

 place by degrees in all the interior parts of the cylinder. For 

 the purpofe of pbferving this change, three vertical holes wereThe changes 

 made in the cylinder, into which were introduced the bulbs of marked by three 



A . - ,, ... _ ^ , , 1 • thermometers at 



three (mail mercurial thermometers. One or the holes was Meq U ai diftanees. 

 the middle of the cylinder; the others midway between the 

 centre and either extremity. 



Each of thefe holes is four lines in ^iameter, and eleven 

 lines and half deep; fo that the bulbs of the thermometers, 

 which are three lines in diameter, were all in the axis of the 

 cylinder. ' ^Io#»uk- 



When the thermometers were put in their places, the holes 

 were filled with mercury, in order to facilitate the communi- 

 cation of heat from the metal to the bulb of the thermometer. 



To keep the hot water conftantly boiling, a fpirit lamp wasfhe one water 

 placed beneath the veflel containing it; and to keep the cold ^P 1 boiling by 

 water conflantly at the temperature of melting ice, frefh por-oth^ cold "by* 

 tions of ice were added to it from time to time. addition of ice. 



Tiie thermometers are graduated to Fahrenheit's fcale, the 

 freezing point being marked 32°, and that of boiling water 

 212". 



As the flrfl and mod important object I had in view was, to The thermome- 

 team at what temperature the three thermometers would be- ters not noticed 



till nearly fta- 

 COme tionary. 



