THERMOMETER. ^207 



is divided by lines furrounding it, or zones, in fuch number as 

 correfpondto the fcale of Fahrenheit's thermometer, viz. from 

 b to 100 degrees. Thefe divifions ought to be engraved on cop- 

 perplate, and a great number of impreffions throvi^n off on 

 finooth or vellum paper, in order that one may be ready to 

 put on each month. 



Fig. 3. MN reprefents the cylinder covered with one of 

 thefe imprefFions. PP is the fcale fixed to the frame on which 

 the cylinder turns. This fcale is divided into 100 of Fahren- 

 heit's degrees, exadlly correfponding to the divifions of the cy- 

 linder. 



Q^is a piece of black-lead pencil, joined to the end of the 

 flot-wire in the place of the knee before mentioned. This pen- 

 cil is made to prefs lightly on the cylinder, by means of the 

 fmall weight R. And as the pencil rifes or falls by heat and 

 cold, it will mark the degrees on the fcale of the cylinder ; and 

 the cylinder being conflantly revolving, the divifion for each 

 day and parts of a day will fucceflively be marked by the pen- 

 cil, which will leave a trace, defcribing an undulated line, di- 

 ftindlly delineating the temperature of each day through the 

 month. Thefe papers, when taken off and bound together, will 

 make a complete regifter of the temperature for the year ; or, if 

 they are parted to one another, they will form a thermometrical 

 chart, by which the variations of heat and cold, during the 

 year, may all be feen and compared by one glance of the eye. 



By infpe(5ling fig. 3. the effedl of the inftrument may be feen. 

 It appears that the paper had been put on the cylinder the firfl 

 day of the month, at midday, when the thermometer flood at 

 45 ° ; that it fell gradually till midnight to 25 ° ; thereafter it 

 rofe till the 2d at 1 P. M. when it flood at 42" ; then it de- 

 fcended at midnight to 2,5^ &c. ; that on the 4th, at midday, it 

 rofe to 50; and at noon, the loth of the month, it flands at 

 40°. 



If 



i. 



