jMagniJjiing Power of Tele/copes. S^ 



plied, and at almoft no expcnfe ; a fmall fcale, a pair of com- 

 paircs, and a piece of paper, being all that is ncceflary. — It 

 n;av be proper, in the firft place, to ftate the fenfe in which 

 I vSc the term magnifying pozut-r of a fclrjcofe; for it is dif- 

 ferently underltood by difi'ercnt pcrfons : alfo to diftingnilh 

 between the object itfelf, and the magnified image of the 

 objeft looked at, as feen in the field of the teiefcope. The 

 difference in fize, between the obje£l viewed with the naked 

 eye and its image as feen in the field of the teiefcope, con- 

 liituting the magnifying power of the teiefcope, the queftion 

 is. How ought this diScrencc to be cxpreffed ? Should it be 

 exprefTed in a comparifon of their refpcftive diameters, areas, 

 or folidity ? For inftancc, if a piece of paper of three inches 

 fquare, croflTed each way by three lines, and thus divided in- 

 to nine fquares, be placed at a diftancc, and viev^-ed by a teie- 

 fcope that caufes one of thofe fquarea to appear as large as 

 the whole paper, at the lame dillance, appears to the naked 

 eye ; if we compare this effect by the dillbrcnce in diameter, 

 we fhould fay, the infiruvient magnifit-s three times: bnt as 

 one fquare appears as large, whenfeen^through the teiefcope, 

 as the whole nine do to the eye unaffifted by that inftru- 

 ment, might it not be aflerted, with equal truth, that it is 

 magnified nine times? The latter appears as reafonable as 

 the former ; but, as in this cafe the paper appears, when 

 viewed by the teiefcope, of the fame dimcnfions as it would 

 do to the naked eye wlien placed at o?ie third the cVtJlance 

 from the chftrver, it is molt ufual to fay, it is magnified 

 three times. Some people, who yet mean the fame thing, 

 fay, but improperly, that it appears three times nearer 

 than it really is. Again, if an objeft at the di fiance of ico 

 yards appears by the teiefcope as large and diflinct as it 

 would do to the naked eve at the dillance of one yard, it is 

 faid to be magnified one hundred times; and it is to l;e un- 

 derfiood in this fenfe in the following experiments: — By a 

 (elcfcopc of the lull mentioned power, a printed paper, at the 

 6 dnlj,nc:c 



