482 Mr. Voulton' 8 further experi incuts upon 



lined with silver paper, which widened to half the circumference 

 at the top. The silver paper roof was domed, the summit extending 

 nearly 1 decimetre above the top of tlie cjdinder. All the silver- 

 paper was well crumpled. In use, the cylinder was placed on a 

 white paper floor, and the clear part of the circumference was 

 turned towards a strong light. The silvered back was highly 

 illuminated, but the inner part of the dome was in shadow, espe- 

 cially its upper part. 



XLVIII. A low wide glass cylinder, 2'63 decimetres diameter, 

 •812 high. Arranged as in XVIT., except that tin-paper was used, 

 and was crumpled, and that roof and back passed gradually into 

 each other. Nearly all sj)ace available. 



XLIX. A bright tin box, similar to XXIX., except that it was 

 not lined with paper, the surface of the tin-plate being used as an 

 environment ; another similar box was also employed hi 1887. 



D. White Sueroundings. 



L., LI. Two white " opal " glass gas globes, 1*78 decimetres high, 

 placed, narrow opening upwards, on a sheet of white paper. The 

 upper open end was provided with a white paper roof. 



E. Clear Glass. 



LII. Eectangular clear glass box about 2*6 decimetres high, and 

 I'G square in section, with open end uppermost, and covered with 

 clear sheet of glass. All angles and edges bound with black 

 paper. Placed in strong light. 



Tliis was also used in the experiments on G. obsciirata, when 

 the clear glass roof was replaced by perforated zinc. 



F. Surroundings of various colours. 



LIII. to LXVI. 14 compartments of a wooden box, 12 of them 

 8"3 centimetres wide, 1"35 decimetres high, and 6"0 centimetres 

 deep ; 2 of them (LIII. and LXV.) were rather wider (9*1 centi- 

 metres). In the centre of the back of all, except LYIL, LIX., 

 and LXIV., a small cardboard box (8*7 centimetres high, 4 wide, 

 and 1*7 deep) was fixed with its long axis vertical. In LVI., 

 however, the box was 7'8 centimetres wide. Each box was covered 

 with paper similar to that which lined the compartment in which 

 it was contained. The object was to provide irregularities of sur- 

 face in the shape of angles, shelves, &c. Clear glass sheets covered 

 the whole box, which was turned towards a strong light. The 

 colours of the compartments were as follows : — 



