A POPULAR ACCOUNT 



tended with circumstances which give it 

 small probability, we shall notice the 

 better substantiated claim of Zacharias 

 Jansen, urged by Borelli, and attested 

 by legal witnesses, who were regularly 

 sworn by the consular magistrates of 

 Middleburg in the year 1655. Zacha- 

 rias Jansen appears to have been a 

 spectacle-maker at Middleburg, and 

 the witnesses were his children, a son 

 and daughter. The son assigns the in- 

 vention to the year 1590, and the daugh- 

 ter to the year 1610. Both, however, 

 agree in the fact of the invention ; and 

 the difference in the dates assigned to it, 

 instead of invalidating their testimony, 

 ought to be considered favourable to its 

 truth, since it shows that no conspiracy 

 existed between them. Other witnesses 

 give the honour of the invention to Jean 

 Lapprey, a spectacle-maker in the same 

 place. 



All these circumstances, considered 

 with reference to the general state of 

 optical knowledge at the time, render 

 it probable that telescopes were con- 

 structed by several persons nearly at 

 the same period, each being ignorant 

 of what had been done by the others. 

 Effects so singular and so brilliant as 

 those produced by the telescope could 

 not be long confined to one country. It 

 will easily be believed, that such an in- 

 strument could not continue a mere toy 

 of amusement, or matter of curious ob- 

 servation to philosophers. Among those 

 who applied it to the great ends of 

 science, the name of Galileo stands fore- 

 most. If we could credit his own ac- 

 count, it would not be more than justice 

 even to assign to this philosopher a 

 share in the honour of the invention, 

 although we cannot concede to him a 

 priority. He states that he was at Venice 

 when a report of the wonderful effects of 

 this discovery was spread abroad. Doubt- 

 ful at first to what degree of faith state- 

 ments apparently so incredible were en- 

 titled, he awaited a confirmation of the 

 intelligence, which he received in letters 

 from Paris. Being credibly assured of 

 the reality of the powers ascribed to the 

 new instrument, but uninformed of the 

 particulars of its construction, he ap- 

 plied himself to the investigation of those 

 particulars, by the aid of the established 

 theory of refraction, and completely suc- 

 ceeded in discovering them. He forth- 

 with applied a convex object-glass, and 

 concave eye-glass, to the extremities of 

 a tube, and directing it to distant ob- 

 jects, found that it rendered them three 

 times as large as they appeared to unas- 



sisted vision. The success of this first 

 attempt stimulated him to further exer- 

 tion, and he constructed a second tele- 

 scope which magnified about eight times. 

 Finally, sparing neither labour nor ex- 

 pense on a subject which seemed to pro- 

 mise results so important, he produced 

 a telescope which magnified thirty times, 

 and with this he discovered the satellites 

 of Jupiter, the solar spots, and other 

 phenomena. 



This account of Galileo's proceedings 

 is given upon his own authority. It does 

 not seem, however, likely that Galileo 

 could have remained in total ignorance 

 of the means which produced the won- 

 derful effects which had excited such 

 general attention. Besides, he acknow- 

 ledges that he did not trust to mere pub- 

 lic report, but received a letter expressly 

 on the subject from " the noble James 

 Badovere at Paris." Of this letter, which 

 was written to inform Galileo on the 

 subject, he does not give the particulars. 

 Is it likely that in such a communica- 

 tion, made to such a man, no allusion 

 would be made to the means of produc- 

 ing the effects described, nor that lenses 

 were not distinctly mentioned ? Add to 

 this, that the general problem of magni- 

 fying distant objects by the modification 

 of the rays of light by refraction or re- 

 flection, or both, which we must sup- 

 pose to be that which Galileo asserts 

 that he solved, is very indeterminate, 

 and such as would be extremely unlikely 

 to be deduced from the general theory of 

 optics as then known. Still less proba- 

 ble is it that of the infinite variety of so- 

 lutions, which so indeterminate a pro- 

 blem admits, he would have chanced to 

 be led to that particular one which had 

 been practised in the north of Europe. 



(9.) The honour of the invention of the 

 astronomical telescope belongs indispu- 

 tably and exclusively to Kepler. In his 

 work on Dioptrics, he distinctly suggests 

 the substitution of a convex eye-glass 

 for the concave one previously used. He 

 shows that in this case the image will 

 necessarily be inverted ; but the advan- 

 tage of an enlarged field of view, in 

 which this instrument excels the Galilean 

 telescope, seems to have escaped his no- 

 tice. To this we may, perhaps, impute 

 the circumstance of Kepler's never hav- 

 ing actually constructed telescopes upon 

 the principle which he suggested, con- 

 sidering, probably, that as they presented 

 inverted images, their use for terrestrial 

 objects would be awkward and inconve- 

 nient, and that they possessed no ad- 

 vantage in astronomical observations 



