PHOTOGRAPHY FOR NATURALISTS. 



point of the rubber tube employed. A very narrow 

 tank is best obtained by the substitution of ordinary 

 gas-tubing, the spaces between glass and rebate 

 being wedged up with thin strips of wood. For 

 carriage the whole may be easily taken to pieces and 

 packed so that the baseboard forms a protection for the 

 glass. The arrangement described has been success- 

 fully employed with a stand camera : a modification 

 will probably occur to the reader in which the base- 

 board is prolonged at right angles to the face of the 

 tank and supports the camera. On such lines a fixed 

 focus system could easily be devised for fair weather 

 use on shipboard, and, as there would be no question of 

 portability, might be fitted with a series of solidly con- 

 structed tanks of varying widths. 



An alternative and equally effective method for the 

 construction of small portable tanks is as follows : Three 



pieces of wood are fixed in the 

 form of a three-sided frame, 

 whose length and height are 

 slightly greater than those of 

 the glass it is intended to em- 

 T == Jf = c ploy, and whose thickness is 



the width of the proposed tank. For really small 

 sizes a similarly shaped frame may be cut out of a 

 solid plank, but it is important that the plank should be 

 properly planed up. Following the line of the frame- 

 work is a piece of small indiarubber tubing, secured in 

 position at S S S S by four tacks, which should not 

 pierce the tubing, but merely clip its edge firmly with 



