12 MR. warington's success. 



vessel then I had succeeded perfectly in keepmg a 

 large number of beautiful livmg specimens in a 

 healthy condition up to the close of 1852. I therefore 

 gave instructions for the making of a small tank as a 

 more permanent reservoir, and one more adapted for 

 carrying on my observations and investigations on the 

 economy and habits of the inhabitants. 



"From the experience I had obtained in my experi- 

 ments with the fresh-water tank, I was induced to 

 modify slightly the construction of this vessel ; thus, 

 at the back, or part towards the light, the framing 

 was filled with slate in the same way as the ends and 

 bottom ; for I had found that the glass, originally 

 employed, very soon became covered with a confer- 

 void growth which had an unpleasing appearance to 

 the eye, and in consequence of which I had been 

 obliged to paint the glass on the exterior to prevent 

 this growth from increasing to too great an extent. 

 It was also an unnatural mode of illumination, as all 

 the light should pass through the surface of the water. 

 The front towards the room and the observer was 

 constructed of plate glass, the whole being set in a 

 stout framework of zinc, and cemented with what 

 is known under the name of Scott's cement, and which 

 I have found to answer for the purpose most admirably. 

 Within this tank were arranged several large pieces 

 of rock-work, thrown into an arched form, and other 

 fragments were cemented in places against the slate 

 at the back and ends, and at parts along the water- 

 line, so that the creatures could hide themselves at 

 pleasure ; a short beach of pebbles was also con- 

 structed in order that shallow water could be resorted 



