36 MICROSCOPIC ILLUSTRATIONS. 



constituting a deep magnifier ; and the consequence was, 

 that we had soon devised for us a triplet, composed of 

 three plano-convex lenses, which is by far the most 

 perfect construction employed in simple microscopes. 

 I may remark, however, that the use of these compound 

 magnifiers is limited to the examining of delicate trans- 

 parent objects which admit of being brought almost in 

 contact with the lens. I may mention another improve- 

 ment, though perhaps rather prematurely, viz. that the 

 achromatic object-glass may be used as a simple micro- 

 scope, and with very great advantage when the magni- 

 fying power is moderate*. 



We now proceed to consider the improvements which 

 have been made in compound microscopes. The com- 

 pound, unlike the simple microscope, in which we look 

 through the magnifier at the object itself, is furnished 

 with a second magnifier, designated the eye-piece, through 

 which the sight is directed, not to the object, but to an 

 image of it, which has been magnified by the first lens, 

 or, as it is called, the object-ylass. Now, we have noticed 

 that the best magnifiers of simple microscopes are in fact 

 compounds, being composed of two or three lenses ; but 

 yet they have not the double action of a compound 

 microscope, even should it be composed of only two 

 lenses. Dr. Goring, however, to prevent any confusion 

 arising between the one and the other, proposed the 



* See Chapter X. 



