228 MASSACHUSETTS AGRICULTUEE. 



turns to dust, if too large the top will not pack even. The size 

 is regulated by the use of a ring as a gauge, — every stone being 

 obliged to be capable of falling through this ring in any direc- 

 tion it may be dropped. Hard stones should be one to one and 

 a quarter, softer ones one and a half and the softest two inches 

 in diameter. Larger sizes give less perfect roads. In loading 

 and otherwise handling macadam, a many and close-pronged 

 pitchfork should be used instead of a shovel, so as not to mix 

 in any earth or sand and to sift out the stone dust and chips. 



The macadam being properly prepared and loaded up, it is 

 spread over the foundation in two or three successive layers. 

 Each layer should be rolled, but the top and last one must be 

 rolled to make a good road. Nor will rolling alone do the work. 

 Two other helps are needed : the use of a binding material, to 

 act as a cement between the broken stone, and sprinkling. It 

 is difficult to prescribe in words just what to use as binding ma- 

 terial and just how much to sprinkle and roll ; common sense 

 will in most cases be a safe enough guide. In the macadamized 

 streets of Paris the rule is to roll till a single piece of macadam 

 placed under the roller, will be crushed, without being pressed 

 into the road surface. Gravel somewhat mixed with clay by 

 nature, but not too much, is probably best as a binding material. 

 Clean coarse sand is very good. Other substances will doj where 

 it would cost too much to procure either of the above. 



The subject of rollers is one demanding some attention. In 

 general, people are apt to over-estimate the value of a roller 

 with respect to its weight. It will be evident on reflection that 

 a roller should be as heavy per inch in length of roller, as a 

 loaded wagon wheel is per inch of tire ; or in other words, if we 

 have a wagon with tires two and one-half inches wide and on 

 each wheel a load of say one ton, the roller should weigh two- 

 fifths ton for every inch in length, or a roller three feet long 

 should weigh about fourteen and one-half tons, or else a wagon 

 as above described would exercise more pressure on the road- 

 bed per square inch than the roller and consequently would cut 

 into the rolled surface and produce ruts. Road-rollers are of 

 two principal kinds : those pulled by horses and those propelled 

 by steam. The latter are for many reasons the best. In the first 

 place they can be made as heavy as desired, without proportion- 

 ally increasing the cost of propelling them, and being self-pro- 



