of Experimental Philqfophy. 345 



tions of nature, explaining, as the logicians 

 cxprefs it, ignotum per ignotius, has been lately 

 proved to be no creature of the imagination; 

 and may be exhibited to the fenfes, under the 

 form of inflammable air. Fire, fubtle as it is 

 in its adivity, and univerfal in its energy, has 

 been traced through all its modifications, mea- 

 fured by different ftandards, and reduced to 

 known, precife, and pqfmanent laws, It is there- 

 fore no jufl: complaint, that intelligent princi- 

 ples are negleifted, and that empyricifm in phy- 

 fics is honoured with exclufive encouragement. 

 Yet, in the prevailing rage for experiments, it 

 cannot be unfeafonable to caution the young 

 adventurer, not to deem the microfcope, the 

 retort, or the air-pump unerring guides to truth; 

 but to profecute his refearches into nature with 

 a modeft convidion of the fallacy of his fenfes, 

 and the limited powers of his underftanding. 

 *' You will wonder," fays Mr. Boyle, in the 

 preface to his effays, " that I fhould ufe fo often 

 *' perhaps ; it feems; 'tis not improbable i words, 

 " which argue a diffidence of the truth of the 

 *' opinions I incline to. But I have hitherto 

 " not unfrequently found, that what pleafed me 

 *' for a while, was foon after difgraced by fome 

 *' further or new experiment." 



Mr. Bewley, an eminent chemifl:, not long 

 fince, informed me, that he concluded the pre- 

 fcnce of the vitriolic acid to be unnecefiary to 



produce 



