2o6 DESCRIPTION of a 



Lli are two indexes, formed of thin black oiled filk, pierced 

 by the fmall wire in fuch a manner as to Aide upwards and 

 downwards with a very fmall force, not more than two grains. 



H, the knee of the float- wire before defcribed, is made to en- 

 compafs the fmall wire between the two indexes, fo that, when 

 the float rifes, the upper index is moved upwards, and, when it 

 defcends, it leaves the upper index ftationary, and puflies down 

 the lower index, which is alfo left ftationary, when the float rifes. 



When the inflrument is to be prepared for an obfervation, 

 the one index is to be pulled down, and the other raifed, by 

 means of a bit of wire bent for the purpofe, until both indexes 

 touch the knee of the float-wire: And, when it is again obferved, 

 the upper index will point out the greatefl degree of heat, and 

 the lower the greatefl degree of cold, fince the time they were 

 fet. 



If this thermometer is to be adapted to a piece of clock-work, 

 in order to record the degrees of heat at each hour and minute 

 of time, it ought to be made of larger dimenfions. The large 

 tube may be 40 inches long, and not increafed in diameter, but 

 the fmaJl tube ought to be enlarged in diameter, and not in 

 'length. By enlarging the tube, which contains the fpirit of 

 wine, in length only, it will be affefted by heat and cold in as 

 fhort a time as that before defcribed. 



It is unneceflary at prefent to explain the clock-work. It is 

 fufEcient to fay, that a hollow cylinder of any light fubftance, 

 7 inches long, and 5 inches diameter, is made to revolve upon a 

 vertical axis once in thirty-one days or a month ; a piece of 

 fmooth or vellum paper is put round this cylinder, palled only 

 at the joining, biit fo as to make it adhere clofe to the cylinder; 

 on this paper are drawn thirty-one equal perpendicular dlvi- 

 lions, numbered at the top i, 2, 3, &c. to correfpond to the 

 thirty-one days of the month, each of which is fubdivided into 

 •fix parts, to anfwer to four hours. The length of this cylinder 



is 



