24 Method of conducting the Canal Surveys. 



Fig. 2. exhibits a portion of the map as constructed from the field 

 minutes. It differs from the field-book principally in the circum- 

 stance of its several lines and angles being reduced to their proper 

 relative positions and dimensions. The explanations therefore which 

 have been given for the one will it is believed, be sufficient for a prop- 

 er understanding of the other. 



The maps were formed on separate sheets of super royal paper, 

 bound in the Atlas style, each volume containing fifty sheets and 

 comprehending about thirty or thirty-five miles of Canal. They were 

 projected upon the same uniform scale of two chains to the inch and 

 the border lines, on each separate sheet, were so drawn relatively as 

 to coincide in direction with the magnetic cardinal points of the hori- 

 zon. The shading and lettering were executed in a superior man- 

 ner and the whole exhibited a style and perfection of finish corres- 

 ponding with the importance of the survey. 



Of the two modes of survey whose merits were canvassed by the 

 commissioners, the one above described, was the one to which, as al- 

 ready stated, the preference was awarded. 



In this method the principal measures in the direction of the length 

 of the Canals, were made upon the base line, situated upon the level 

 and even surface of the towing path, under circumstances, it will be 

 conceded, in the highest degree favorable for accuracy ; while in the 

 other mode the measures would have been subject to all the errors 

 arising from inequalities of ground, and the various obstacles to be 

 met with upon the outlines, such as trees, fences, streams. of water, 

 ravines, swamps, rocks, &z;c. which occur more or less frequently upon 

 all portions of the Canals ; add to this, the absolute impracticabili- 

 ty of making such a survey in the many places where the Canal is 

 bounded on both sides by impassable swamps, as is the case at the 

 Cayuga marshes, or is separated as it frequently is, from an adjoining 

 river, by a high terrace wall or embankment, or is bounded upon the 

 berm side by a steep and thickly wooded side-hill, or by lofty and 

 precipitous rocks, similar to what is seen at the Little Falls, at Flint 

 Hill, at the Big Nose, or at the Cohoes upon the Mohawk and at va- 

 rious other places. 



In the method, as pursued, the base or governing line, is located 

 upon the inner edge of the lowing path, the best defined, and for the 

 purpose of general reference, unquestionably the most permanent 

 part of the Canal. The importance of maintaining a hard and even 

 surface for the horse track, renders it necessary to construct it of ma- 



