DEPARTMENT OF MARINE BIOLOGY. 



235 



as characterize limestone surfaces now exposed. Along the edge of the sub- 

 merged cliff are also features somewhat like small stream-cut gulhes but unlike 

 them in being of irregular depth and width, in these respects resembling the 

 features produced by wave attack where the effect is locally concentrated. In 

 places, as for example just west of Bird Key, are larger features strongly 

 suggesting deep, narrow, branching valleys. Other forms characteristic of 

 land areas were sought, but none was found and probably none should be 

 expected. 



Mr. Hector von Bayer, engineer and architect of the U. S. Bureau of Fish- 

 eries, who has charge of the installation of the Bureau of Fisheries Station 

 at Key West, has supplied detailed information on an extensive bed of sub- 

 merged peat, encountered in dredging a channel to the site of the laboratory. 

 He has given us the following statement : 



"In response to your request for data on the geologic formations encountered while exca- 

 vating a channel 6 to 7 feet deep at mean low-water and 30 feet wide, leading from off-shore 

 between the western end of Cow Key and Key West Island to the site of the marine biological 

 laboratory of the Bureau of Fisheries, a distance of about 1.12 nautical miles, I beg to state 

 as follows: 



"So-called marl, fuU of small shells, was generally found at the bottom in 1 to 2 feet of 

 water at mean low tide, with underlying hard oohtic rock, having a flint-like crust; the rock 

 was also frequently encountered bare at that depth. The marl ranged in thickness from 1 

 to over 3 feet. In a number of places, from 300 to 500 feet in length, it was bedded on strata 

 of peat overlying and apparently filling depressions in the surface of the ooUte. The peat 

 ranged from 1 to over 4 feet in thickness, and extended to more than 8 feet below sea-level." 



Later we lent Mr. von Bayer a mud sampler for sounding the peat, and he 

 reported his results, as follows : 



"a. In channel, water 7^ feet deep at m. 1. 1., excavated through 2 feet of marl overlying 

 peat. Bottom of the peat at three locaUties respectively 10.5, 12, and 13 feet below m. 1. 1. 



"b. 100 feet west of the preceding, water 1 foot 9 inches deep, marl 2 to 6.5 feet deep, hard 

 rock at 7 feet, no peat." 



The accompanying figure shows the precise position of the borings into the 

 peat and a diagrammatic section at the locality. 



Section at point 



marked A 

 (mean low tide) 



r^ 



Scale in yards 



m 



Fig. 1. — Soundings in feet, mean low water. Map traced from U. S. C and G. chart No. 584. 



The upper surface of the oolite has a crust precisely similar to the incrusta- 

 tion usual on the rock subaerially exposed. In fact this crust is apparently'as 

 significant and as definite evidence as is the submerged peat. 



