APPARATUS AND METHODS. 



a knitting-needle may be used as a rod, and it may be 

 either fixed into a piece of wood or passed through the 

 cork of a short wide bottle filled with shot. Two simple 

 forms of lens holder, supplied by Messrs. Flatters and 

 Garnett, are shown in Figs. 1, 2. 



Fig. 2. A Lens Holder, on heavy base, with slow-focussing 

 adjustment and two ball-and-socket joints. 



3. Black and White Plate for Dissections, etc. 



(Fig. 3). Get a piece of thick glass, and paste or glue on 

 one side of it a piece of white paper or card, half of which 



is painted black. Keep 

 the papered side down, 

 place on the upper side 

 the objects to be exam- 

 inee! with the lens, and 

 move them along so as 

 to see their appearance 

 against the opaque white 



Fig. 3. Black-and-white Tile, for dissections, and black Surfaces. 



Specially prepared glazed 

 black-and-white tiles can 

 be purchased. 



A glass plate prepared 

 in this way, but with the middle third left transparent, 

 can be mounted on a wooden frame made by removing two 

 sides of a box ; in the bottom of the frame place a piece 

 of mirror, slanted so that the transparent middle portion 



on one side, and with concentric circles 

 for arranging parts of flowers in the form 

 of a floral diagram. 



