Instnuiwnls of t lie Aid'wnh, ?1 



hand, to finde nought but ayr. Hereby have some men 

 (in all other matters counted wise) tbuly over-s)iot them- 

 selves : misdeeming of the means." — Here it is observable 

 that Dec does not, "as in the former quotaLion, affirm that 

 he nctuaUij saw tlicsc effects of perspective prcjdueed. The 

 lord chancellor iJfira?^ relates, that his great precursor and 

 namesake, Roger Bacon, apparently walked in the air be- 

 tween two steeples, which he supposed was the etfect of 

 reflection from glasses, while he really walked on the 

 ground *. And w hat Dee savs of the " shew of Gold, 8cc." is 

 apparently taken from the b\\\ chapter of Roger Bacon s tract 

 De Niiliilate Magice ; though 1 do not find that the great 

 author is mentioned, or alluded to, in this whole preface. 



19. But the most extraordinary passage la this jjerfurm- 

 ance of Der, is the following: — '* No small skill ought he 

 to. have, that should make true report, or neer the truth of 

 the numbers and sunnnes, of footmen or horsemen, in the 

 Enemies ordering- Afarre off, to make an estimate between 

 neer terms of More and Lesse, is not a thing very rife, 

 among those that gladlv would do it." — " The Herald, 

 Pursuivant, Serjeant Koyall, Captain, or whosoever is care- 

 full to come neer the truth herein, besides the Judgment 

 of his expert eye, his skill of Ordering Tflc//cff//, the help 

 of his Geometricall instrument : Ring or Staffe Astrono- 

 micall : commodiously framed for carnage and use.) He 

 •may wonderful I ij hell) himself' hy perspective Glasses, In 

 which, (I trust) our posterity will prove more skilfull and 

 expert, and to greater purposes, tlaan in these dayes, can 

 (almost) be credited to be possible." 



20. I apprehend that this last passage must be admitted 

 as a decisive proof, that " perspective glasses," and some of 

 their most useful effects, were known in England, in 15/0; 

 or more than 40 years earlier than 1609, or I6l0, when 

 they are commonly believed to have been invented ia Hol- 

 land. I say more than 40 years ; for Dee here talks of them 

 as we should do of instruments familiarly known, but in the 

 use of which we were not so " skilful and expert" as, we 

 *' trusted, our posterity would one day prove ;" probably be- 

 cause thev had not yet been reduced to a very commodious 

 form. Thus much the words of Dee clearly warrant us to 

 iiffirm ; but how muck more than 40 years, they do not au- 

 thorize us to say. Nor will Dee's words enable us to ascertain 

 whether his " perspective glasses" were dioptrical or catop- 

 trital ; for his definitions above inserted, of " perspective" 



* Set Dr. Uuii'jn's Mathematical Dictionary, article Optics. 



B it and 



