244 



THE AMERICAN MONTHLY 



[Aug. 



provided for them in the trap door. The under horizon- 

 tal edge of the frame is provided with a scraping blade 

 standing out and directed a little downward. This facil- 

 itates the penetration of the mud tlirough the mouth of 

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

 net there is another brass plate called the weight plate 

 on which weights are placed to increase the specific 

 weight of the ajoparatus. These weights are required 

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



cal position and thus they prevent the 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 fine wire tissue round the 

 frame to which the gauze is fixed. 



The net (b) is conical; and consists of tine gauze. It is 

 fastened to the border of wire tissue surrounding the 

 backside of the frame. 



The apparatus is carefully let down by the aid of the 

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



