Chap. 7.] DefeRs of Sight, how remedied. 



With a fmgle glafs the defects in fight, with refpe<5t 

 to many objects either too near or at too great a dif- 

 tance, for the perfons labouring under them, are re- 

 medied i but there are cafes where the object is fo far 

 diftant or fo minute, that though its outline may reach 

 the eye, its parts muft ftill, even with the aid of a 

 fingle lens, be indiftinctly perceived. The art of man 

 has difcovered a remedy, in a great degree, to this im- 

 perfection, and by means of a combination of glaffes 

 has opened a wide field for his refearches into the won- 

 ders of nature ; he can now trace the limbs of an in- 

 fed invifible to the naked eye, or he can make the ce- 

 leftial objects appear to him as if their diftance had 

 been on a fudden diminifhed by mhny millions of 

 miles. 



