244 



THE AMERICAN MONTHLY 



[An. 



proi'ided for tlicm in the trap door. The uminr horizon- 

 tal ed^e of tlie frame is provided with a scraping blade 

 standiufi: ont and directed a little downward. This facil- 

 itates the penetration of the mud through the mouth of 

 the frame into the net. Opposite to this and inside tlie 

 net there is anotlier brass plate called the weight plate 

 on which weights are placed to increase the s[)ecific 

 weight of the ajjparatus. These weiglits are roquiied 

 for maintaining the apparatus, when let down, in a verti- 



cal position and thus they prevent tlie frame from lying 

 down by its own weight. There is a strong ring on the 

 semicircular part of the frame, to which the puUing-line 

 for lifting and lowering the apparatus is fastened. 

 Beside this there is a border of line wire tissue round the 

 frame to which the gauze is fixed. 



The net (b) is conical; and consists oi line gauze. It is 

 fastened to the border <>r wire tis^n." snvrdiiiidini': the 

 backside of the frame. 



Tlu' apparatus is carefully let down by the aid of the 

 rope. At the same time the rope which is fiistened to the 



