FARMERS' INSTITUTES. 47 



fifteen feet is abundantly wide for a double track road. Twelve hun- 

 dred cubic yards of stone will be required to build a good nine foot 

 road, and two thousand yards will be required for the fifteen foot road. 

 Crushed cobble stones will make five and one-half cubic yards for each 

 cord when measured in two or more grades. 



For country roads stone must be provided in at least two grades. 



The coarser stone may be all that part of the product passing over a 

 seven-eighths inch screen and through a two and one-half inch screen. 

 These stones should be placed upon the road uniformly mixed. For 

 most country roads a six inch depth of consolidated stone will be ample, 

 while in some cases six inches of loose stone making four and one-half 

 inches after compacting will be sufficient. To make six inches of con- 

 solidated stone road, the stone should be applied in two layers. 



Apply the bottom course after the bed has been perfectly shaped and 

 rolled till hard, to a uniform depth of four inches. Koll dry till smooth 

 and apply the screenings, being all that part of the product of the 

 crusher which passes through the seven-eighths inch perforations of the 

 screen, to a depth of about three-fourths of an inch. Apply water with 

 a sprinkling wagon and roll till thoroughly consolidated. 



After the bottom course is finished, put on the second or top course 

 in the same manner, except that a small surplus of screenings should 

 be applied to the top course. Water copiously and roll thoroughly; 

 apply new screenings as the others disappear, being careful to keep the 

 coarser stones covered, but do not use an excess of screenings. Con- 

 tinue the rolling till the water flushes to the surface and till fragments 

 of rock will crush beneath the roller before penetrating the road. 



Before the rolling is finished the shoulders should be smoothed down 

 and the whole bed thoroughly rolled from gutter to gutter so as to 

 make a uniformly crowned surface. 



Crushed lime stone from the various quarries of Michigan form ex- 

 cellent material for the lower courses of macadam roads. If cheap 

 enough it would be advisable to use them for the full depth of all roads 

 where the trafflc is not too severe and where the dust does not prove 

 seriously objectionable. The best results, however, have been produced 

 by using crushed cobble stones for the surface and, these are to be 

 recommended for all sections where they are abundant and where the 

 price does not make the use prohibitive. 



Repairs. — As in gravel roads repairs should be constant, never allow- 

 ing ruts to form. Stone should be applied in small quantities, only 

 enough to fill the slightest depressions being used. The best results are 

 secured by applying stone for repairs in wet weather. Early in the 

 spring and late in the fall are the best times. Stone for repairs should 

 range in size from one-half inch to one inch. Large stones and dust 

 are to be avoided. 



