[ 388 ] 



It may be objeded, that mercury rifes to great heights above its 

 natural ftate even in fummer, when no fuperior tropical effluence 

 prevails, which is certainly true ; but it muft be remarked, that a 

 vaft acceffion of air arifes in that feafon from the decompofition of 

 water in growing vegetables, as Dr. Hales has abundantly proved, 

 and is now univerfally acknowledged. Nay, Melander Hielm in- 

 forms us, that the quantity of air emitted from gun-powder dur- 

 ing a battle raifes mercury in barometers fituated in the vicinity. 

 5 Nev. Schwed. Abhandl. 1784, p. 9. Nor (hould we fufped that 

 the atmofphere fhould thus receive an annual increafe, as much is 

 deftroyed by volcanos, tornadoes, hurricanes, and putrefying fub- 

 ftances, &c. 



Most of the particulars I have advanced, relative to the influ- 

 ence and difference of the fuperior currents, receive the fulleft con- 

 firmation from Euler's fynoptical table of the variations of the ba- 

 rometer during the month of May, 1769, in the vaft empire of 

 Ruffia, including an extent of obfervation, amounting to nearly 

 4000 miles, from the weftern parts of Ruffian Lapland to lakutz 

 in Siberia, and eleven degrees from north to fouth. The places 

 where the cotemporaneous ftates of the barometer were obferved 



were* : 



* This table I have here copied from the 14th vol. of the N. A6ta Petiopol. 



Latitude. 



