Chemical and Physical Notes 1 1 1 



and it is further imagined that the height of the barometer 

 at each of these stations is found to be the same, namely, 

 735-5 millimetres. 



If we assume that the force of gravity is the same at the 

 sea-level in all latitudes, then the fact that the atmosphere 

 everywhere exercises the same pressure as a certain standard 

 length of mercury, is evidence that the mass or the quantity 

 of air in a column of the atmosphere having the same base is, 

 at the sea-level, everywhere the same. If the height of the 

 standard barometer had not been the same at each of these 

 stations, and at the same time it was known that the force of 

 gravity did not vary, then the conclusion would be necessary 

 that the quantity of air in the atmospheric column at the 

 sea-level is greater in one latitude than in another. 



If the height of the standard barometer is, as postulated 

 in the table, the same at each of the stations, and if it is 

 known that the force of gravity is not constant, then the 

 height of the standard barometer of itself gives us no in- 

 formation regarding the pressure of the atmosphere. The 

 constancy of the height of the standard barometer justifies no 

 other conclusion than that the pressure of the atmosphere is 

 different in different latitudes. 



If the law of the variation of the force of gravity with 

 change of latitude is known, then the constant height of the 

 barometer allows us to arrive at the relative pressure of the 

 atmosphere at different latitudes. If, in addition, the absolute 

 value of the force of gravity at any one latitude is known, 

 the constant height of the standard barometer enables us to 

 conclude what is the absolute pressure of the atmosphere at 

 the different latitudes. 



If the distribution of matter in the earth is homogeneous, 

 and if the force of gravity at the sea-level varies, then the 

 conclusion is necessary that different stations at the sea-level 

 are at different distances from the centre of the earth, or they 

 are at different altitudes, referred to this point as fundamental 

 datum. 



If the law which connects the variation of the force of 

 gravity with distance from the attracting centre is known, the 



