368 



Biologij in America 



reflection too is greater the greater the depth, so that at 

 depths of a few hundred feet daylight may last but a few 

 minutes, wliile at de])ths of more than 3,000 feet is a realm 

 of perpetual niglit. The character of the sea also, whether 

 smooth or rough, materially affects the results — the rougher 

 the surface, the greater the number of mirrors, placed at many 



and eonstantly changing angles, 



and the greater the reflection of 

 the light. 



In collecting samples of water 

 from various depths of the sea 

 for chemical analysis, o'r for 

 studying the microscopic life 

 which it contains, various types 

 of "water bottles" are em- 

 ployed. These can be closed at 

 the desired depth and the con- 

 tained sample then drawn to the 

 surface for examination. The 

 type in most common use at 

 present is the Eckman bottle, 

 another piece of apparatus de- 

 signed by the naturalist, V. W. 

 Eckman, to whom reference has 

 already been made. This is a 

 reversible instrument consisting 

 essentially of a metal cylinder 

 with two lids. In lowering the 

 cylinder the two lids are held 

 open so that water can pass 

 freely through it. After it has 

 reached the desired depth a mes- 

 senger is sent down the line re- 

 leasing a catch, when the cyl- 

 inder upsets itself by its own 

 weight and the lids are auto- 

 matically closed at the same time. 

 Held in the frame beside the 

 water bottle is a reversible ther- 

 mometer, so that the apparatus serves for taking water samples 

 and temperatures at the same time. A second messenger 

 may be attached to the bottom of the frame in such a way 

 ihi\\ when the first messenger reverses the bottle, the second 

 messenger is released, which in its turn reverses a second 

 bottle and thermometer at a loAver level, and so on. In this 

 way a number of simultaneous observations may be made 

 on a single line. 



JiiGELow Water Bottle 



With deep sea thermometer 

 reversed at the right, and ' 

 sengcr" at top. 



CourtvHji of flir 



V. S. liurcau o} Fisheries. 



mes- 



