208 MASSACHUSETTS AGRICULTURE. 



posed to accommodate ; that is, from the admissible grades, 

 radii of curves, &c. Given two points it is desired to connect, 

 vrith no intermediate point where the road is to touch, that 

 route is the best which will cost least to build and maintain, the 

 grades and curves being kept within bounds ; and to find this 

 location constitutes the whole problem of the engineer. 



The Romans built all of their roads in perfectly straight lines, 

 up hill and down, at a very great expense, as being absolutely 

 the shortest distance between two points. At a later period in 

 history, it was argued that a road must be winding to be agree- 

 able, and many were so built only for this reason. The modern 

 road-builder or engineer in general, ignores any such consider- 

 ations, and has for his aim only to achieve the most, at the least 

 present and future expense. 



As regards curves in roads in a hilly or mountainous district, 

 we have then the rules never to make a smaller radius than 

 20 feet, and that only in extraordinary cases. On roads where 

 long logging or other wagons may be expected, the smallest 

 radius ought to be 50 or 60 feet ; and, in general, 40-45 feet is 

 none too much. 



A rule sometimes followed in constructing mountain roads, 

 is, where the inclination is 1 or 2 in a hundred,* heavy teams 

 require 40' and light ones 30' radius ; with a grade of 2 or 3 in 

 a hundred, heavy teams require 65' and light ones 50' radius. 

 Where a reverse curve (shaped like the 

 letter S) occurs, there should be a straight 

 piece connecting the two curves, (Fig. 1.) 

 On the contrary, where the 

 two curves to be connected , 

 FIG. 1. ^i"G concave in the same di- 



rection, the connecting link should be curved 

 also, and not straight, (Fig. 2.) On the length 

 of the curves the grade should be made easier 

 than on the parts of the road immediately ad- 

 joining. ^'^^- 2- 



As regards grades, to start with mountain paths, we find 

 pedestrians able to walk up an inclination of 100 in 120 ; 



* In describing grades, tlie first figure gives the vertical height which is 

 ascended in a horizontal distance given by the second figure. Both figures 

 must of course be taken to refer to the same unit of length, thus : 100 feet 



