Birge—A Second Report of Limnological Apparatus. 
551 
The construction of the sampler is plain from the figure. The 
base of the apparatus is made of heavy sheet brass, about 30 cm. 
by 7 cm. The sample tubes are ordinary hard-glass test tubes, 
2.5 cm. by 20 cm., fitted with a rubber stopper which is pierced 
with one hole. The tube is held in place by a rubber-covered 
spring clamp. The sample tube is sterilized and then exhausted 
with an air pump, and the small inlet tube is sealed off with the 
blow pipe. The point of the inlet tube rests between two jaws 
and is broken by the blow of the brass messenger which is sent 
down the line and strikes the movable jaw. 
In all of our work we have used sample tubes closed by rubber 
stoppers. We have found these entirely satisfactory for depths 
up to those of Lake Mendota—25 meters—and we have used them 
without difficulty up to a depth of 60 m. in Green Lake. In 
deeper water a glass sample tube can be used, which has been 
drawn out and sealed; but unless the depth makes such an ar¬ 
rangement necessary, the stoppered tube will be found much more 
convenient. 
