74 Proofs from old English Books, that the 



refracting telescope, though, Galileo excepted, not one 

 of them had any correct ideas of the theory ; and there- 

 fore Bacon's mistakes in that theory, or in any other 

 part of his subject, can have no weight against the fact, 

 proved by many parts of his writings, that he was ac- 

 quainted with the dioptric or refracting telescope. This 

 argument applies to every branch of science. Kepler's total 

 ignorance of the theory of the laws which bear his name, 

 can have no weight against the fact that he discovered those 

 laws, and knew that they prevailed in the solar system. 

 Dr. S. himself submits to the force of this argument on 

 another occasion. In his 03d remark, he expresses his 

 surprise that " the ancients could not account for burning 

 by reflection from a concave metal 1" yet he acknowledges 

 that " they knew and cultivated catoptrics :" and (Remark 

 121.) that they had burning mirrors. 



27. In his il?)th remark, the doctor asserts that Bacon 

 " was not qualified to invent a telescope, by experiments, 

 lor want of lenses." — " I have shown above," says he, 

 " that he never had handled a convex spectacle-glass."—^ 

 With what force the doctor has shown this, I must leave 

 to the reader of his 88th remark. But is it probable that 

 such a man as Bacon, ivithout theory, would make an 

 «* attempt upon making spectacles," as the doctor owns he 

 did (Bern. 118), and yet not be able to produce some sort of 

 a spectacle-glass ? — In this same remark Dr. S. quotes a 

 passage adduced by Dr. Jebb, to show that Bacon was no 

 stranger to the astronomical use of the telescope. It is 

 this : Seel huge magis quam hcec : oporteret homines haberi, 

 qui bene, immo optime, scirent perspectivam et instrumenta 

 ejus, — quia instrument a astro?wmice non vadunt nisi per 

 vhiionem secundum leges istius scientiee. Dr. S. gives no 

 translation of this passage. It may, however, be rendered 

 thus ; ci But what is much more (important) than these 

 things ; men ought to be had who understand perspective* 

 and its instruments well, yea exquisitely well ; — because 

 the instruments of astronomy only proceed by vision, ac- 

 cording to the laws of that science." Dr. Campbell tells 

 us that this passage is in the Opus Tertium, and he very 

 naturally considers it as a proof, iC that he (Koger Bacon) 

 made use of the telescope in his astronomical observations." 

 And certainly, a great force of reasoning would be ne- 



* In Bacon's time, and tonsj after it, by the word Perspective was 

 meant Optics in general, as is evident from the quotations in the former 

 past of tins, tetter. 



cessary 



