86 J. T. COOK ON A SIMPLE TROUGH FOR POND LIFE. 



in halves ; also a piece of hard wood, such as mahogany, f in. 

 thick, and from this cut a piece 6 in. long and 1 in. wide. Next 

 cut a shallow groove about | in. deep along one of the edges just 

 sufficiently wide to take the two pieces of glass. Then divide 

 the slip of wood into six sections, which will provide material 

 for three troughs. A small rubber ring, preferably square in 

 section, is placed between the glass slips in the position shown 

 in the figure, and the edges of the glass slips are then fitted into 

 the grooves in the edges of the square of wood, in such a way 

 as to hold the rubber ring in position and to render it water- 

 tight. Should the grooves be insufficiently wide to receive 

 the glass slips, they may be increased slightly in width by the 

 use of a flat file. The writer has kept specimens of pond life 

 in these troughs for many weeks simply by adding a small 

 quantity of fresh water every other day. The lower figure 

 represents a trough in which the glass slips used are 3 x IJ in., 

 and by their use a larger trough is obtainable. Of course, in 

 this case the original slip of wood is 1| in. wide instead of 1 in. 

 as in the smaller size described above. They are only intended 

 for use with low powers up to say J in. ; but as much of the 

 work on pond life is done with 1-in. objectives, they will be 

 found very useful. The advantages of such a trough are found 

 in their extreme simplicity and cheapness ; any one can make 

 them, also they can be taken to pieces for purposes of cleaning 

 without any fear of breaking. 



Joum. Queketl Microscopical Club, Ser. 2, Vol, XIII., No. 78, April 1916. 



