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a problem which before its invention muft have appeared far 

 beyond the reach of human abihties, has been determined. It 

 was this inftrument, which in the hands of Otto Guericke and 

 our immortal countryman Mr. Boyle, fuggefted the invention and 

 improvement of the air-pump, and thus paved the way for the 

 numerous difcoveries to which this latter gave birth. To this 

 inftrument we ftand indebted for our knowledge of the clafticity, 

 condenfation and rarefadion of the air ; properties which have 

 fince been fo happily applied to the conftrudion and improve- 

 ment of hydraulic machines, and the menfuration of heights. 

 To it we owe a more accurate knowledge of the laws of the 

 vibration of pendulums, and of thofe of the refradion of light ; 

 difcoveries from which aftronomy, and confequently navigation, 

 have -derived the greateft advantage. Nay, it may with truth be 

 afferted, that it is to this inftrument that modern philofophy 

 owes its exiftence, and modern Europe its fuperiority over all 

 other regions ; for it was the Toricellian experiment that firft 

 demonftrated the futility of the antient mode of philofophifing, 

 and the advantages of experimental inveftigation, and thus ex- 

 cited the more civilized nations to thofe purfuits, which have 

 fince rendered them as fuperior both in arts and arms to the 

 more ignorant, as men are to brutes. 



Great, however, as has been the fuccefs attendant on the 

 ftudy and application of the obfervations made by the help of 

 the barometer, the bulk of mankind have always expedcd ftill 

 more from it : Nothing lefs indeed than a prognoftic of the 

 weather. Nor is this expcdation entirely vain ; particularly in 

 the circumftance in which fuch foreknowledge is of moft impor- 

 tance. 



