PRACTICAL PHOTOMICROGRAPHY. 



157 



is limited, because the number of subjects suited to the instru- 

 ment is limited. The loss of light in projecting a large image 

 of even a moderately thick object is so considerable, that only 

 in exceptional cases can success be expected. Moreover, as 

 our optical science now stands, the combined difficulties of 

 great magnification, illumination, resolution, and definition are 

 too great to be satisfactorily overcome, except in specially 

 favorable circumstances.* 



FIG. 36 (a). 



The instrument known as an optical (or vulgo "magic") 

 lantern is quite common and its appearance familiar to every 



* Since this was written the author has seen a greatly improved instru- 

 ment by the same makers and for the same purpose. It is, however, 

 costly. It is shown in Fig. 36 in its latest and best form. 



