306 



NOTES ON A MAP INTENDED TO ILLUSTRATE 



very far these efforts have fallen short of any general survey of the United States. Ill 

 fact, they have made no impression whatever upon its vast central area. 



It is a portion of this central area that I desire to characterize by the map which 1 ex- 

 hibit this evening. 1 have drawn it on stone, from a photographic copy of a large wall- 

 map, which I constructed at the instance of Mr. T. E. Blackwcll, when Managing Direc- 

 tor of the Grand Trunk Railroad in Canada, in 1861. One of the most public-spirited 

 and enlightened men that ever crossed the Atlantic, Mr. Blackwcll had been occupying 

 himself and ten or twenty assistant observers, for several years, with the meteorological 

 and commercial statistics of the Lake Country, intending to embody these in a memoir on 

 the Hydrology of the St. Lawrence 1 , partly to gratify his own professional zeal and taste 

 for natural science, but more to enlighten his countrymen on subjects connected with the 

 future prosperity of America, of which he was an enthusiastic prophet. Mr. Blackwell's 

 father had been in a previous generation at the head of the profession of civil engineering 

 as applied to canal construction and waterworks in England ; and the son, brought up in 

 the pursuits of the father, and inheriting his abilities, was the acting efficient junior mem- 

 ber of the commission of three appointed for devising a new system of drainage for the city 

 of London. His untimely death, after a journey in Egypt, where, although a sad invalid, 

 he filled his note-books with the most telling and instructive geological sketches of that 

 country that it has ever been my good fortune to see, prevented the appearance of his me- 

 moir before the Institute of Civil Engineers, for which it had been prepared, and was the 

 means of its being published ultimately in the Transactions of the American Philosophical 

 Society, of which Mr. Blackwcll had been elected a member only a year or two before his 

 death. 



During the final revision of the materials for this memoir, I spent two months, as his 

 finest in Montreal, furnishing him with geological data to exemplify the subject ; and our 

 discussions led us to design a second memoir, on the Iron Resources of the United States, 

 to be illustrated by a map, showing not only the positions of the American Iron Works, 

 but also the belts — the geological belts — of ore-bearing formations, upon which their ex- 

 istence depended. This afforded me an opportunity to realize an old and favorite design. 

 Accordingly, 1 compiled a map of the United States, fifteen feet square, giving my own 

 interpretations of the published topography of every State which exhibited marked fea- 

 tures of relief, — basing these interpretations, first, upon the authentic topography of the 

 State of Pennsylvania ; secondly, upon my own topographical notes in other States ; thirdly, 

 on numerous local and county maps ; fourthly, on the better marked portions of the State 

 maps ; and lastly, on the colored geological maps of the several States, or parts of States, 

 already published. 



The result was very striking. Eamiliar as I have been for years with the topography 



