EXAMINATION OF MARINE OBJECTS 99 



as the work proceeds, but the parts, having a tendency to float, 

 readily separate from one another and therefore become more 

 distinctly visible when submerged. 



A very convenient form of trough may be made by taking any 

 kind of rectangular, flat-bottomed dish, one made of zinc being, 



FIG. 48. SHEET OF CORK ox THIN SHEET LEAD 



perhaps, the best of all, and covering the bottom with a slab of 

 good cork carpet which has been weighted with sufficient lead to 

 prevent it from floating. Or, instead of cork carpet, a sheet of 

 cork may be used. In either case, a piece of thin sheet lead, a 

 little larger than the slab, should be cut, the corners of which are 



FIG. 49. WEIGHTED CORK FOB DISSECTING TROUGH 



then snipped off as shown in fig. 48, and the edges finally turned 

 over as represented in the next illustration. The size of the 

 trough must be regulated according to the nature of the work to 

 be done, but one measuring ten inches long, seven wide, and two 

 inches deep will answer most purposes. 



