AND EXTERNAL RESISTANCE. 313 



Subsist in a vaporific, or gaseous form, in the 

 form of rain, or in a dry state : it will be found 

 that the weight and inelasticity of the one, will 

 far exceed the levity and expansibility of the 

 other : in the one case, the mercury in the tube 

 sinks in the other it rises, while the degree of 

 depression of the mercury is found in a great 

 measure to depend on the decompositions, 

 which the atmosphere undergoes, from dryness 

 to moisture from a calm to a storm ; its ele- 

 vation, on the contrary, proportionably takes 

 place, from moisture to dryness from astorm to 

 a calm. From the experiment of Perrier, which 

 I have detailed, and which has been repeated 

 by different metereologists, it appears, that the 

 elevation of the Anaplometer, to 3,000 French 

 feet, from the surface of the earth, occasioned 

 a depression 3:1-8 French inches of the mer- 

 cury; from whence it was concluded, that 

 3 : 1-8 inches of mercury, weigh as much as 

 3000 feet of air, and 1-10 f an inch of mer- 

 cury, as much as 96 feet of air ; when, there- 

 fore, the mercury stands at 30 inches, near the 

 sea shore, it is conjectured, that, if it were 

 raised to 300 times 96 feet, or a little more 

 than five miles, the mercury in the tube would 

 sink to the same level in the basin, as it is 

 found to do, in the receiy^, after the greatest 

 portion of air which it captained, has been ex- 

 hausted out of it. In order to make the calcu- 



