CHAP. 9. OF TEMPERATURE. 



CHAPTER IX. 



SOME MISCELLANEOUS OBSERVATIONS ON AT- 

 MOSPHERIC TEMPERATURE AND PRESSURE. 



AFTER the invention of the Barometer and 

 Thermometer, many important discoveries, about 

 the Pressure and Temperature of the atmosphere 

 were made by philosophers. The knowledge, 

 however, of their variations, and the relations of 

 these variations with other phaenomena, remains 

 still very obscure, and leaves a wide field for 

 future investigation. 



When Galilaeo and Torricellus had discovered 

 that the Pressure of a column of atmosphere was 

 equal to that of a column of mercury of equal 

 base, and of about thirty inches of height, and 

 to a column of water of the same base, and 

 about thirtyfive feet in height : but that the 

 height of the mercury or water, which balanced 

 the column of air, varied a little at different 

 times, philosophers began to measure the atmo- 

 spheric pressure by such means ; and finding 

 that its variations were very irregular and 

 uncertain, and were not referable to any known 



R 2 



