8 ANIMAL LIFE UNDER WATER 



In consequence of his helpful criticisms all 

 the subaqueous observations and photographs 

 in this book were made under such circumstances 

 that the rays of light from the object observed 

 struck the glass of the observation chamber or 

 apparatus at right angles; refraction and conse- 

 quent distortion have thus been reduced to a 

 negligible quantity. 



A description of my first observation pond 

 was given in " Marvels of Fish Life," published 

 by Cassell's in 1911. This consisted of a con- 

 crete pond with an observation chamber below 

 the level of the water in one bank of the pond. 

 No light entered this chamber except through 

 the surface of the water. Life in the pond was 

 therefore observed illuminated as in Nature. 

 Further, in consequence of the light in the pond 

 and the darkness in the chamber, the glass 

 became a mirror to a fish, and the observer, if 

 clad in dark clothes, was entirely invisible to 

 the denizens of the pond. 



The observations and illustrations in this 

 book have been made from ponds built on the 

 same principle, but, as I have stated, the glass 

 windows of the observation chambers have been 

 fixed at various angles so as to avoid distortion. 



