MICROSCOPIC OBJECTS. 171 



similar to those described above, but having an adjust- 

 ment for limiting the opening and closing of the blades, 

 which is effected by means of screws or shdes. The 

 scissors described above may readily have this adjust- 

 ment by passing a loop of thin wire around the handle 

 and arm near c. 



(22.) Eye-shades for looking through Microscopes. — It 

 is necessary when we examine with one eye an object 

 through an instrument, not to permit any excitement on 

 the other, and to shade it from surrounding hghts. In 

 compound microscopes this is easily done by a large disc 

 of card-board, having a hole in its centre, placed over the 

 eye end of the instrument ; but the best plan for general 

 purposes is to have a pair of spectacles with a thin black 

 disc in one aperture, and the other empty, as here 

 shown : — 



(23 .) Candlestick for Microscopic Purposes. — It is very 

 desirable with artificial light, to be able to turn it about 

 in any position : this may be effected by employing a 

 candle- or lamp-holder, similar to either of those shown 

 in the engravings in page 172. The candle in either is 

 capable of being raised or lowered as may be required, 

 and that having the condenser serves also to illu- 

 minate opaque objects with a strong light. 



