LECTURES. 



ON ROADS AND BRIDGES. 



BY FAIR MAN ROGERS, 



PROFESSOR OF CIVIL ENGINEERING IN THE UNIVERSITY OF PENNSYLVANIA. 



FIRST LECTURE. 



It is the business of the civil engineer to design and to execute the 

 public works of a country, and of such works the means of communi- 

 cation are, perhaps, the most important. In some countries this 

 branch of the engineer's profession is taken as a type of the whole 

 range of his duties; and we find in France the "Corps des Ponts et 

 Chaussees" is not confined necessarily to the consideration of "bridges 

 and roads" only, but extended to the many branches which we include 

 under the name of "civil engineering." 



I shall devote these lectures to an examination of the principles 

 which govern the location and construction of roads, and of the 

 bridges, which, under ordinary circumstances, form an important part 

 of them. 



In any country, no matter how new, means of communication be- 

 tween different settlements of men, or between any points of resort, 

 are of the first necessity. Where all traveling is done on foot, as was 

 the case in our country while occupied by the Indians, simple trails 

 marked by blazed trees to indicate the direction, will be sufficient. 

 When beasts of burden are introduced, a wider and smoother path is 

 necessary, and road making on a small scale commences; obstacles 

 which the hunter on foot easily surmounted must be removed for the 

 pack horse. In many rough countries, such as Switzerland and Spain, 

 bridle paths were the only avenues of communication until within a very 

 recent period, and many of these are in use at the present day. In very 

 mountainous countries, even the construction of a bridle path requires 

 a considerable amount of labor and ingenuity, as is shown in most of 

 the Swiss passes — such as that of the St. Bernard, the Tete Noire, and 

 particularly the Gemmi. 



As sledges or wheeled vehicles, even of the rudest description, come 

 into use, the roads must be made wider, smoother, and less steep, until 

 we come to the limits which are now assigned by engineers for roads 

 of the first class. 



It would seem hardly necessary to dilate upon the immense advant- 

 ages which spring from ample and economical means of communica- 

 tion throughout a country. In this age of rapid locomotion, they are 



