V2 MARVELS OF PONn-l.IFE. 



before commencing a microscopic examination ; this 

 is a practical and pliysiological mistake. Nature 

 meant both eyes to l)e open, and nsnally resents a 

 prolonged violation of lier intentions in this mat- 

 ter. It requires but a little practise to keep 

 l>oth eyes open, and only pay attention to what 

 is seen by thjit devoted to the microscope. The 

 acquisition of this habit is facilitated, and other 

 advantages gained, by a screen to keep out extra- 

 neous light. For this purpose take a piece of thin 

 cardboard about nine inches square, and cut a 

 round hole in it, just big enough to admit the 

 tube of the microscope, about two inches from the 

 l)ottom, and equidistant from the two sides. Next 

 cut off the two upper corners of the cardboard, and 

 give them a pleasant-looking curve. Then cover 

 the cardboard with bbick velvet, the commonest, 

 which is not glossy, answers best, and your screen 

 is made. Put the hole over the tube of the 

 microscope, and let the screen rest on the little 

 ledge or rim which forms an ornamental finish to 

 most instruments. A piece of cork may be gummed 

 at the back of the screen, so as to tilt it a little, 

 and diminish its chance of coming into contact 

 with that important organ the nose. This little 

 contrivance adds to the clearness and brilliancy 

 of objects, and is a great acconmiodation to the 

 eves. 



