Sentence:  ... I think I may presume that what I have hitherto Diſcourſed will induce you to think, that Chymists have been much more <WSD>happy</WSD> in finding Experiments than the Cauſes of them; or in aſſigning the Principles by which they may beſt be explain'd. 
Meaning of the word marked with <WSD> tags:  Experiencing the effect of favourable fortune; favored by fortune or luck; fortunate, lucky, propitious.