16 THE MICROSCOPE. 



focus, and present the object that is to be 

 viewed in a perfectly colourless, or white light. 

 Unimportant as this improvement may seem 

 to us, it baffled the most eminent men of science 

 to accomplish it until within these twenty-five 

 years. " When it is considered," says Dr. Car- 

 penter, " that in the highest powers now made, 

 the largest of three pairs of lenses is very little 

 larger than a pin's head, and the smallest much 

 smaller than a pin's head, we can easily under- 

 stand the difficulty of producing the required 

 achromatic corrections in these cases, and ad- 

 mire the marvellous mechanical skill to over- 

 come in such a space the difficulty of chromatic 

 aberration/' 



9. How important the results flowing from 

 the invention of such lenses ! Through an open- 

 ing, large as the prick of a pin might make, 

 they revealed to us new worlds, and the extra- 

 ordinary structures of many of the most delicate 

 and beautiful objects in nature. What Young 

 said of the human eye, we may well apply to 

 the Microscope, which 



" Takes in at once the landscape of the world 

 At a small inlet, which a grain might close, 

 And half creates the wondrous world we see." 



