1894.] Microscopical journal. i69 



found, generally at a depth of from four to eight feet. In 

 digging for foundations of abutments of bridges or cul- 

 verts, especially in salt marshes, diatomaceous earth is 

 almost invariably thrown up, and, as I have before men- 

 tioned, ditches dug foi drainage will often give oppor- 

 tunity for interesting finds. All these, however, belong 

 to the chapter of happy accidents, and should not be al- 

 lowed to limit the operations of the collector. The great 

 majority of diatomaceous deposits lie buried and will 

 never be brought to light except by explorations under- 

 taken for that purpose. Under nearly every large 

 swamp whose level surface shows that it occupies the 

 bed of a former lake or pond lies a deposit of diatoms ; 

 in very dry seasons some of these may be reached by 

 digging, but in many cases the water makes this diffi- 

 cult and some kind of boring apparatus will be useful. 



I have a cheap home-made contrivance that answers 

 the purpose in most cases. It consists of a cylinder of 

 galvanized iron about four inches in diameter and some 

 eighteen inches long, slightly flaring toward the top ; 

 the lower edge is sharpened and provided with an in- 

 ternal lip on one side, one inch wide and three inches 

 long, inclined spirally upwards. This is to prevent the 

 enclosed core of earth from slipping out when it is 

 drawn up through the water, and it also helps in pene- 

 trating through the deposit. On opposite sides at the 

 top are riveted stout flat strips of iron which extend up- 

 ward to a socket in which fits the handle, keyed in so as 

 to be easily removed. The handle is a stout pole of the 

 necesary length, with a cross bar at the top. 



In using this I first investigate the swamp and decide 

 which were the deeper parts of the former lake, then I 

 dig down with a spade as far as as easily practicable; 

 then I commence boring. As soon as the cylinder is 

 filled I draw it up and empty it out at the top and exam- 

 ine carefully. As soon as the black muck changes to a 



