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GEOLOGY OF THE FOURTH DISTRICT. 
Trigonometrical Survey and Map of Niagara Falls. 
The accompanying map has been constructed from a very careful survey by Mr. Blackwell,* 
giving the present position and outline of both falls, and the river banks upon either side. 
Upon application to His Excellency Sir Charles Bagot, late Governor-General of Canada, I 
was authorized to establish monuments upon the Canada shore, and was also kindly offered 
every other aid to promote the objects of the survey. These monuments, together with those in 
New-York, will enable future observers to ascertain the amount of recession during any given 
period. In places where the rock is exposed, copper bolts have been fixed, and in other places 
hewn stone monuments. The starting point for all these observations is a copper bolt fixed in 
the rock on the north side, near the edge of the American fall; the trigonometrical point No. 
1, is thirty-nine feet four inches north, 80° east from this. These points are connected with 
T. P. No. 2, so that in the event of those nearest the cliff being undermined, the latter can be 
resorted to. The accompanying table of observations will serve to reconstruct the map so 
long as any of the points remain. 
The following are some of the elevations noted at the time of this survey : 
Height of American falls, October 4th, 1842,. 167.70 feet.f 
Height of Canada or Horseshoe fall,. 158.50 “ 
First terrace, height above top of fall at the point before mentioned,. 14.75 “ 
(The surface of this terrace is uneven, with scattered fragments of limestone, 
appearing like the bed of a river.) 
Second terrace,... 24.09 c< 
Third terrace,. 32.42 “ 
Fourth terrace, (the one containing shells),. 39.79 “ 
This terrace slopes upward to the railroad, a height of. 46.20 “ 
General level of Goat island, corresponding to that of the fourth terrace,. 39.86 “ 
Top of highest terrace at whirlpool,. 70.00 “ 
Base of this terrace, or level of the bank at the same place,. 46.98 “ 
Shells were found in a fine clayey loam at the whirlpool, at an elevation of ... 33.03 “ 
More abundant at. 35.00 “ 
And continuing upward to. 46.00 “ 
♦This survey was made in the fall of 1842, though the observations had been principally made by Mr. Blackwell in 1841; but 
as no permanent monuments had been established, it was thought better to review the whole. Through the kindness of Mr. Fay, 
the resident engineer at Lockport, Mr. Gibson and Mr. T. Evershed were directed to accompany me, and, together with Mr. 
Blackwell, to make the requisite observations and run the levels, all of which are shown upon the map. 
t This elevation is from the level of the water below the falls to the copper bolt near T. P. No. 1. The elevation varies from 
four to twenty feet with the elevation of the water in the river below the falls. 
