BY WAY OF INTRODUCTION 9 



My observations have also been checked by 

 means of a swinging apparatus, with a mirror at 

 the bottom, which served as a periscope under 

 the water. 



Finally, a box apparatus has proved useful 

 as a telescope for direct downward observation. 



These different forms of observation are dia- 

 gramatically shown on the accompanying plate. 



For the observation of objects in the water a 

 vertical glass is used, as shown in No. 1 ; while 

 for recording the appearance of objects on and 

 above the surface the " window " is fixed at 

 various angles as shown in 2. In 3 and 4 two 

 forms of box cameras are illustrated for under- 

 water photography, with the photographer above 

 the level of the water. A temporary box 

 observation chamber is shown on the lower illus- 

 tration on this plate. This box when in use was, 

 of course, covered by a lid. It will be seen that 

 the supply of water into the observation stream 

 was controlled through a pipe. 



I would next draw attention to the value of 

 reflection as a concealing factor under the water. 

 In Chapter III of " Marvels of Fish Life " I 

 dealt fully with this subject, and showed how this 

 reflection was modified by counter-shading and 



