644 



SCIENCE. 



[N. S. Vol. IX. No. 227. 



the sediment and the size and velocity of 

 the stream transporting it. Owing to the 

 fact that observations as to the amounts of 

 the fine clay-like detritus of glacial streams 

 are more numerous and reliable than those 

 upon the coarser material, the bulli of the 

 contemporaneous claj's was taken as a basis 

 of calculation, rather than the sand-plain 

 itself In estimating the load of the glacial 

 stream, I have taken the maximum value 

 of 13 gi-ams per liter, given by Reid for 

 the Muir Glacier (the highest value on 

 record), as the one which, in all probability, 

 would most nearly correspond to the load 

 of a glacial stream during the closing stages 

 of the continental ice sheet. 



At the time of the formation of the Har- 

 rington clays the land stood at a level of at 

 least forty feet below that at present exist- 

 ing, and the deposition took place in an in- 

 closed bay, having the ice sheet as its 

 northern boundary, a ridge of till and 

 modified drift for its eastern boundary, 

 and an earlier sand-plain as its southern 

 boundary. On the west was a broad and 

 deep opening, connecting with Narragansett 

 Bay, and admitting of a complete com- 

 mingling of the salt and fresh waters. Into 

 this inclosed bay flowed a stream with a 

 width, as indicated by its esker, of 150 feet, 

 a depth of some 20 feet, and an average 

 velocity of not over 5 feet per second. On 

 the assumption that the amount of sedi- 

 ment was 13 grams per liter, the daily dis- 

 charge of clayey material would have been 

 some 526,500 tons j)er day. 



Experiments recently conducted by Pro- 

 fessor W. O. Crosby in connection with 

 professional work for the Metropolitan 

 "Water Board of Massachusetts, the results 

 of which he has kindly placed at my dis- 

 posal, indicate that material such as the 

 clay beds are essentially composed of, i.e., 

 quartz-flour, settles with great rapidity, 

 and it can be shown that practically the 

 entire amount of sediment brought in by 



the glacial stream must have been deposited 

 within the inclosed bay described. 



The clays cover about a square mile in 

 area, have a maximum thickness of 60 feet, 

 and a total bulk of 95,300,000 tons. Divid- 

 ing this bulk by the daily discharge of sedi- 

 ment by the glacial stream (526,500 tons), 

 the time of deposition of the clays is indi- 

 cated to have been 181 days, or almost ex- 

 actly six months. 



The Barrington deposits probably repre- 

 sent very nearly average conditions ; hence 

 a period of six months seems a fair estimate 

 of time for the formation of a simple sand- 

 plain of moderate sixe. In the case of large 

 plains, with areas of several or many square 

 miles, the period of deposition may be con- 

 sidered as extending over more than one 

 season of melting, there being in the mean- 

 time either no retreat of the ice margin or a 

 retreat so slight that the intervening space 

 was completely filled and the sand-plains 

 united into a single compound plain. 



Myeon L. Fuller. 



PROPOSED SURVEY OF THE NILE.* 

 The Egyptian government has agreed to 

 undertake a survey of the Nile with the 

 object of determining the species of fishes 

 inhabiting its waters. It is due in the first 

 instance to the efforts and energetic action 

 of Dr. John Anderson, F.R.S., who has al- 

 readj' done so much to enlarge our knowl- 

 edge of the fauna of Egypt that this impor- 

 tant project, to which so much scientific 

 interest is attached, has now taken definite 

 shape. A memorandum prepared by him, 

 setting forth his proposals for the survey and 

 the lines of his scheme for carrying it out, 

 received the approval of Lord Lister, Presi- 

 dent of the Royal Society ; Professor E. Ray 

 Lankester, Director of the Natural History 

 Departments of the British Museum; Dr. A. 

 Giinther, President of the Linnsean Societj^, 

 and Mr. P. L. Sclater, Secretary of the 

 *From the London Times. 



