CONFERENCE OF GOVERNORS. 91 



It has been found by long experience that, where it is possible 

 to avoid it, a gradient of over 6% per cent, should not be permitted 

 on a stone road. I can see no objection to a 6% per cent, gradient, 

 where the cost of reducing it seems unwarrantable. It is un- 

 necessary to say that a maximum of 5 per cent, is better, but in 

 many parts of the country the cost would be too great. It has 

 been determined that on an ordinary macadam road in the country 

 the crown should be from % to % of an inch to the foot ; for a 

 greater camber than this carries the water ofE too fast, and compels 

 vehicles to travel in the center of the roadway, thus wearing out 

 the center more rapidly than any other part, and tending to rut it. 

 A less crown will not permit of proper surface drainage, under 

 ordinary circumstances. 



Whether a road is to be built of gravel or of stone, the provisions 

 for the drainage of its sub-grade and the removal of surface water 

 should be precisely the same. Where good gravel can be obtained 

 at reasonable cost, and where the nature of the traflBc is such that 

 more durable or expensive material is unnecessary, it may be better 

 to build a road of gravel than of broken stone. Ordinarily the 

 cost of a gravel road is much less than that of a macadam road, 

 and it is more agreeable to ride over. 



It has been found that the most economical method of building 

 culverts in Massachusetts is by using reinforced concrete; or, 

 where small pipe culverts are necessary, reinforced concrete ends are 

 built. The reason for this is, that with the reinforced concrete 

 very much thinner walls can be built, and the cost for transporta- 

 tion and for materials is very much reduced. It has been found 

 that for bridges reinforced concrete beams can be used economically 

 and safely up to a span of from 30 to 40 feet, and that for over 

 that length the span arch construction should be adopted. A bridge 

 built of concrete, when properly constructed, with a concrete floor, 

 offers the vast advantage of giving a permanent structure which 

 requires no repair. 



It has been the practice of this commission to use much care in 

 the roadside work, both in removing unsightly earth, stone and 

 other obstructions, and objectionable trees or brush, and in thinning 

 out and cutting the native growth, so as to produce a roadside 

 growth which is not only ornamental but advantageous. It is 

 recognized that a certain amount of shade on any road is bene- 

 ficial to the road and also agreeable to the senses. For this reason 

 the commission has established a nursery for the growth and 

 propagation of many kinds of trees which are later transplanted 



