440 Professor J. W. Spencer—Recession of Niagara Falls. 
be repeated to almost any extent without damaging the specimen, so 
that it would be a simple matter for any worker to send a set to all 
his correspondents, or better still to the chief museums. 
Professor Nathorst suggests that the method may also prove of 
service to zoologists, whether neontologists or paleontologists. 
Certainly it might sometimes enable one to study delicate ornament 
and to obtain photographs of it with greater ease, especially when 
the specimen itself is of a dark colour or irregularly spotted with 
colour. Some of the minuter Bryozoa, or colonial Hydrozoa, or 
Stromatopores, might perhaps lend themselves to this treatment. 
I have myself laid in a stock of collodion solution and intend to use 
the method as occasion offers. Meanwhile it is hoped that the 
publication of this note will direct the attention of other workers 
in this country to what promises to be a valuable aid to the 
paleontologist. 
IlJ.—Recrsston or tHe Niagara Fatts.! 
By Professor J. W. Spencer, A.M., Ph.D. 
OR many years Niagara Falls and the Great Lakes of America 
have been special subjects of my researches. These at last have 
been completed under the Commission from Dr. Robert Bell, acting 
Director of the Geological Survey of Canada, and later of Mr. A. P. 
Low, Director, with results beyond anticipation. These were obtained 
through precise instrumental measurements, borings, and soundings, 
not hitherto undertaken. 
My recent survey of the crest-line (1904-5), compared with that of 
Professor James Hall, 1842, shows the mean rate of recession to have 
been 4:2 feet a year, with the average breadth of the gorge produced | 
by the falls being 1200 feet. But a longer record (agreeing with the 
more recent) has been found by Mr. James Wilson and myself in 
discovering the position of the Falls in 1678, from the crude 
description and picture made by Father Hennepin at that time. 
Between 1890 and 1905 the rate of greater recession diminished. 
I succeeded in making soundings under the Falls and throughout 
the Gorge by the use of Tanner-Blish self-registering tubes, depending 
upon the hy drostatic pressure, as the current was too strong. for the 
use of an ordinary line. At the Whirlpool, and at some other places, 
it was necessary to work from a cable swung across the Gorge. 
Under the Falls themselves, the sounding tubes were inserted in 
a specially designed buoy which the force of the Fall drove down to 
the rocks, that had collapsed beneath the Falls themselves. These 
were reached at 72 feet, while the floor of the river beyond varied 
from 84 to 100 feet below the surface of the river. Farther down, 
there was a lateral inner gorge, reaching to 192 feet, which could 
not have been produced by the present descent of the Falls. An 
explanation of this, however, was found. 
1 Read before the British Association for the Advancement of Science, Section E 
(Geography), Leicester, August, 1907. Abstract. 
