Telescope, &c. were Jirst known in England. 77 



mistry and other subjects, he' called in the aid of <e experi- 

 mental perspective and practical astronomy *." — f( On the 

 other hand," continues Dr. S. in this same 120th remark, 

 (C he conceives some effects of telescopes which cannot pos- 

 sibly be performed by theSm;" The best answer to this is, 

 that, as is above observed, Dr. S. himself mentions, in his 

 1 I7th remark, Porta's folly in believing that Ptolomy could 

 see ships 600 miles off; yet the doctor, in his 104th remark, 

 allows Porta's pretensions as an inventor (or, as I should 

 say, a re-inventor) of the telescope, to pass without animad- 

 version. The truth is, that the ardent spirit of inventors is 

 but too apt to deal in prodigies; and I see no reason to 

 exempt either Bacon or Porta from the common infirmity 

 of their brethren. What wonders and H exuberances" 

 were to be, and still are to be performed, in our own times, 

 by air-balloons, and galvanism, and the gases ! . 



29. Dr. S. sums up the evidence on Roger Bacon's pre- 

 tensions to a knowledge of the telescope in his 121st re- 

 mark, which is as follows : ie If it be asked, How Bacon 

 came by these notions ? I answer, From the common doc- 

 trine of refractions in his canons, and from common ap- 

 pearances by refraction and reflection; especially from con- 

 cave speculums, whose effects were well known to him, 

 both by the accounts of them in antient authors, and by 

 his own experience. And this I take to be a sufficient 

 ground for a man of good sense and fancy to produce all 

 that he has said. I conclude, then that the time of the inven- 

 tion of telescopes was not earlier than the beginning of the 

 17th century." — After what has been stated (though not 

 so perfect as could be wished) the reader will probably be 

 inclined, as I am, to substitute for this conclusion of Dr. S. 



is. 8d. and in France, before the revolution, to about io'd. all estimated 

 in. parts of the Troy pound weight of fine silver. (See Henry's Hist, pf 

 G. Britain.) By Sir Geo. Shuckburgh Evelyn's excellent table in the 

 Philosophical Transactions for 1798, 60I. in the year 1250 was about 

 equivalent to 562I. in 1800; so that Bacon's first burning-glass may be 

 said to have cost him about 187I. and that he laid out on Uli experiments, 

 &c. in 20 years, about 18733!- of our present money. 



* Cum adjutorio schntue expeririienialn peppectii'*, et astronomic opr- 

 ra/iva', &c. p. 9. Exurpta ex Lib^o Sexto Siuntlaium, qvem jecit tratcr 

 Rognus Bacon , prefixed to Sanioris Medicine Magistri. D. R-g-ri Bacc'nis 

 Angliy Thesaurus Cbemicus, Franeofurti, 1620. Bacon's connecting per- 

 spective (optics) with practical astronomy, as he does on other occasions 

 also, is very remarkable, and will no duubt be regarded by some as. :t 

 strong presumption that sciences, which he thus connected in his lan- 

 guage, he also united in his yractice ; for practical astronomy can no 

 more exist without optics than navigation can without them both. 



4 ' that 



