344 MR BLACKADDER on Meteorological Instruments 



ether may be requisite ; but, on most occasions, rain-water is 

 sufficient ; the use, however, of common ardent spirits for such 

 a purpose, is attended with but a trifling expence, and may be 

 found convenient. 



Having thus shown how the temperature of the air and other 

 bodies may be determined, during absence, and at any given in- 

 stant, it may readily be conceived, how it may, in like manner, 

 be determined at successive intervals of time, by multiplication, 

 and fitting arrangement of the same means. Thus, omitting va- 

 rious less complete combinations, seven thermometers of the be- 

 fore-mentioned construction, connected by a very simple piece of 

 mechanism, will enable us to determine the exact temperature 

 every hour during the whole course of the day and night, and 

 that with very little trouble. For, to obtain this, it is neces- 

 sary to inspect the instrument only three times in the course 

 of the day, or during that period not usually appropriated to 

 sleep ; for example, at 7 A. M., 4 p. M., and 11 p. M. 



It must be obvious, however, that there is nothing to pre- 

 vent the number of inspections being reduced to one in the 

 twenty-four hours, if there was a sufficient reason or motive for 

 doing so. 



The instrument for registering the hourly atmospheric tem- 

 perature, and which is now exhibited to the Society, is intended 

 to be fixed on the outside of a window. It must be evident, 

 however, that the dimensions are much greater than are at all 

 necessary ; for if constructed by an expert workman, the mecha- 

 nism connected with the thermometers might be reduced to 

 about the size of a common musical snuff-box. 



Having thus endeavoured to describe a method of register- 

 ing the indications of the thermometer at any given instant, and 



