AND EXTERNAL RESISTANCE. 311 



fall of the mercury in the Anaplometer, by the 

 known changes which the atmosphere under- 

 goes, concluded, that the weight of the atmos- 

 phere was greatest when it was most serene and 

 clear ; and, on the contrary, that it was most 

 light, when most thick and cloudy and charged 

 with vapours ; that is to say, that it was most 

 heavy when it was most light, and most light 

 when it was most heavy ; the mercury rising 

 in the former case from 26 to 30 inches ; and, 

 on the contrary, settling in the other from 30 

 to 26 inches. 



It was owing to the same errors from which 

 conclusions have been drawn, revolting to the 

 feelings and to the senses of the most ignorant, 

 that the pressure of the atmosphere upon bodies 

 situated near the surface of the earth, was the 

 pressure of weight, not of expansibility; and 

 that the weight of the incumbent column was 

 said to be the cause of that compression ; inso- 

 much, that if there were a pit dug in the bow- 

 els of the earth, 33 miles in depth, the air at 

 the bottom would be as dense as water, but if 

 it were 50 miles deep, the air would, in that 

 case, be as dense as gold itself. It was in fur- 

 therance of this false philosophy, that it was 

 affirmed, and continues to be believed at this 

 time as a true article of philosophical faith, 

 that the absolute weight, or perpendicular pres- 

 sure downwards of the atmospheric column 



