276 Dr. H. A. Nicholson on Dredgings in Lake Ontario. 



XLII. — Preliminary Report on Dredgings in Lake Ontario. 

 By H. Alleyne Nicholson, M.D., D.'Sc, M.A., F.K.S.E., 

 Professor of Natural History in University College, Toronto. 



In consequence of the interesting discoveries made in the 

 dredgings carried on in Lake Superior in the summer of 1871 

 in the U.S. steamer ' Search' (Reports of the Sec. of War, 

 U.S. vol. ii.), I was induced to apply to the government of the 

 Province of Ontario for a grant to be expended in prosecuting 

 a similar series of dredgings in Lake Ontario, a lake which 

 had hitherto never been explored by the dredge. With a 

 praiseworthy appreciation of the value of such scientific re- 

 searches, the necessary assistance was generously granted to 

 me by the Provincial Government ; and the results obtained 

 are of a very satisfactory character. The short time, however, 

 which has elapsed since the dredging was completed has not 

 permitted more than the most hasty examination of the mate- 

 rials collected. In the following preliminary report, therefore, 

 I shall merely state the general results which were obtained, 

 reserving for a future occasion a detailed account of the animals 

 which were collected. 



The dredgings were all carried on in the later part of June 

 and the early part of July, and were made partly from the 

 yacht ' Ina ' and partly from the steamer ' Bouquet.' They 

 were entirely carried on by hand ; and the dredges employed 

 were such as are ordinarily used in sea- dredging. In dredging 

 in deep water, however, a bag of embroidery canvas Avas 

 attached outside the ordinary net — an addition rendered neces- 

 sary by the extremely fine nature of the mud at great depths, 

 i^ven with this precaution the dredge not unfrequently came 

 up nearly or quite empty from great depths, its contents having 

 been completely washed out. In deep water, also, a fifty-six- 

 pound weight was attached to the rope, at a distance of about 

 12 feet above the dredge ; and the same was necessary in 

 shallow water where the weeds were very thick, in order to 

 secure that the dredge should reach the actual bottom. 



The dredgings were all carried on within a radius of ten 

 miles from Toronto ; and the following will show the general 

 nature of the bottom at different depths, and the chief loca- 

 lities at which the dredgings were prosecuted. 



In Toronto Bay itself numerous hauls were made, both from 

 the yacht and the steamer, and the bottom proved very varied, 

 though the depth is almost constantly from 2 to 3 fathoms. 

 The greater portion of the bay, comprising the central part 

 of its area, has a bottom which appears to consist uniformly 

 of a tenacious, exceedingly fine, clayey mud, the temperature 



