optics, 297 



that is, in words, one egg of an ostrich is equal to 

 fifteen million six hundred and twenty-five thou- 

 sand eggs of a mite. And there is great reason to 

 believe, that there are eggs of other animalculae 

 far less than those of a mite. Indeed, the greatest 

 stretch of the human mind is insufficient to ex- 

 plore the amazing and inconceivable gradations 

 in every part of Nature ; and nothing but the all- 

 piercing eye of boundless Intelligence can see 

 through a series of such infinitely decreasing pro- 

 gressions. 



It may be here worth noticing, that a telescope 

 is easily converted into a microscope, by removing 

 the object-glass to a greater distance from the eye- 

 glasses; for the distance of the image varies with 

 the distance of the object from the focus, and is 

 more magnified, as its distance from the object is 

 greater: the same telescope may, therefore, be suc- 

 cessively turned into a microscope with different 

 powers. Botanists might find some advantage in 

 attending to this; it would assist them in dis- 

 covering small plants at a distance, and thus often 

 save them from the thorns of a hedge, and the 

 dirt of a ditch. 



Telescopes. 



In a refracting telescope, the glass which is nearest 

 the object in viewing it is called the object-glass ; 

 and that which is nearest the eye is called the 

 eye-glass. The object-glass must be convex, but 

 the eye-glass may be either convex or concave; 

 and generally, in looking through a telescope, the 

 eye is in the focus of the eye-glass, though that Is 

 not very material; for the distance of the eye, as 

 to distinct vision, is indifferent, provided the rays 



