AND EXTERNAL RESISTANCE. 303 



the absurdity, that equal effects can be produc- 

 ed by unequal causes, or that the weight of 25 

 or 30 grains can accomplish as much as the 

 whole incumbent weight which the atmosphere 

 is falsely supposed to possess : if the receiver, 

 with which the first instrument was covered, 

 be removed, and exposed to that supposed 

 weight, the mercury within it continues unal- 

 tered. The conclusion, therefore, presses upon 

 the mind with force irresistible, that the eleva- 

 tion of the mercury in the Torricellian tube, 

 and the various degrees of elevation and de- 

 pression which it undergoes, are not caused 

 , by the weight or gravity of the air ; and 

 that the weather-glass now in general use, 

 called barometer, from 0f nfyov, a meter or 

 measurer of weight, is called by a term 

 which is irrelevant and improper, but that 

 the term ana-plometer, from the compound 

 word avaKKou ftfyov, a meter or measurer of expan- 

 sibility, ought to be substituted for it. So far, 

 therefore, from the barometer measuring the 

 degree of pressure which the atmosphere exerts 

 by its weight, it is by its expansibility alone 

 that the atmosphere acts, pressing with the 

 greatest force when it is least ponderable, and 

 when it is most ponderable exerting the least 

 pressure; that is to say, that it is most expan- 

 sible when least ponderable, and least ponde- 

 rable when most expansible. 



During the various discussions which I have 



