392 Fly-rods and Fly-tacJde. 



of glass was inserted, inclining slightly inward from the 

 perpendicular. The tank was painted a dark slate color 

 without and within. It closely resembled a coffin with 

 parallel sides, and its advent excited considerable inter- 

 est both in the neighborhood and in the household itself, 

 since it was delivered in my absence, and I had thought- 

 lessly omitted to give any intimation of its expected ar- 

 rival. A stand was also provided, which, when the tank 

 was placed upon it, raised its bottom about three and 

 a half feet from the ground. 



The whole apparatus was set up in the back-yard, dis- 

 tant forty feet from the house, which bore nearly east 

 from it. To the westward the nearest building was about 

 one hundred and twenty feet distant, while to the north 

 and south there were none nearer than several hundred 

 feet. Thus the tank was located as nearly as possible in 

 the middle of the space enclosed within an ordinary city 

 block of houses, and perfectly open to the sky. Its length 

 lay nearly north and south. From about half-past eight 

 o'clock in the morning until about five o'clock in the af- 

 ternoon it was unshaded from the sun. 



Having filled the tank with water, the first problem 

 attacked was to determine how trout see objects above 

 the water. That they were able so to do I had often 

 seen demonstrated, not always to my entire satisfaction. 



As heretofore intimated, if any one will look through 

 one of the side glasses of an ordinary aquarium, and up- 

 ward towards the surface of the water, they will find that 

 surface to resemble polished silver, and to be totally 

 opaque to vision. Objects lying above it are as invisible 

 as though a stone wall intervened. Or the experiment 

 may be more conveniently tried with one of those thin 

 uncut glass tumblers now in fashion. Half fill one with 



