258 Reglfer Thermometer. 



cylinder, of any light fubftance, feven inches long, and five inches diameter, is made to re- 

 volve upon a vertical axis once in thirty-one days, or a month ; a piece of fmooth or vellum 

 paper is put round this cylinder, parted only at the joining, but fo as to make it adhere clofe 

 to the cylinder ; on this paper are dravm thirty-one equal perpendicular divijions, 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 anfvirer to four hours. The length of this cylinder is divided by 

 lines furrounding it, or zones in fuch number as correfpond to the fcale of Fahrenheit's ther- 

 mometer, namely, from O to lOO degrees. Thefe divifions ought to be engraved on copper- 

 plate, and a great number of impreffions thrown off on fmooth or vellum paper, in order that 

 one may be ready to put on each month. 



Fig. 3, M N reprefents fthe cylinder covered with one of thefe impreffions. P P is the 

 fcale fixed to the frame on which the cylinder turns. This fcale is divided into loo of Fah- 

 renheit's degrees, exaftlycorrefponding to the divifions of the cylinder. 



Q_is a piece of black-lead pencil joined to the end of the float-wire in the place of the knee 

 before mentioned. This pencil 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 conftantly revolving, the divifion for each day 

 and parts of a day will fucceffively be marked by the pencil, which will leave a trace defcribing 

 an undulated line, diftindly delineating the temperatureof 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 pafted 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^ting fig. 3, the effe£t of the inftrument may be feen. It appears that the papers 



had been put on the cylinder the firft day of the month at mid-day, when the thermometer 



ftood at 45° ; that it fell gradually till midnight to 25° ; thereafter it rofe till the 2 at i P. M- 



when it flood at 42° i then it defcended at midnight to 35° ; then on the fourth at mid-day 



' it was to 50^" ; and at noon the tenth of the month it ftands at 40". 



If three inches be added to the length of the cylinder, it may be made to delineate the va- 

 riations of the barometer as well as the thermometer, and thereby to form a complete chart 

 or view of the progrefs of both of them. And if inftruments of this kind were kept in dif- 

 ferent parts of the country, and their charts compared together, it would afford much informa- 

 tion with regard to meteorology. 



On 



