IOO NEW YORK STATE MUSEUM 



prevent the screenings from being picked up by the wheels of the roller 

 if you apply the water and allow it to settle down below the top surface 

 before passing the roller over it. Too much water, or too little, will give 

 trouble by causing the surface to be picked up. 



You must not under any conditions roll the screenings while dry. 



You must not under any conditions allow teams to pass over the road 

 after the screenings are spread and before they are rolled. 



In case of a deficiency in the water supply, you may have the screenings 

 spread and await a rain before rolling; but in such case the road must be 

 entirely closed to travel, and the rolling must be begun as soon as the 

 road is wet and continue until the section covered with screenings is 

 thoroughly compacted. In such cases it may be necessary to operate the 

 roller day and night, and you must insist on this being done. In case 

 you meet with any difficulty in compacting the stone, and fail to under- 

 stand the cause, report immediately in writing to the office. 



Telford. Telfording will be used in all cases where the road passes 

 over clay, or wet soil. You will make a careful study of the road, and 

 report in writing to the chief engineer where in your opinion telfording is 

 needed, giving a description of the soil, together with the general scope 

 of the adjacent ground. In your report you will note the stations be- 

 tween which the telfording may be needed. 



Where telford is to be used, you will see that the road bed is excavated 

 and carefully rolled, and left true and even, corresponding to the cross- 

 section, and 12 inches below the established grade of the finished work. 

 You will then cause 2 inches of gravel to be uniformly spread over the 

 sub-grade. On this sub grade you will place a foundation of stones, 

 which may vary in size as follows : 4 to 10 inches in width, 6 to 20 inches 

 in length, 5 to 6 inches in depth (not more than 10% of the stone to be 

 less than 6 inches in depth). The stone must be sound, and of a quality 

 approved by the chief engineer. 



The telford stones shall be placed by hand, vertically, on the broadest 

 edges and lengthwise across the road, so as to form a close, firm pave- 

 ment. They shall be bound by inserting and driving down, in all places 

 where it is practicable, stone of proper size and shape to wedge them in 

 their proper position. No large stone will be left with a projecting point 

 coming nearer than 4 inches to the finished grade and cross-section. If 

 any such projection be found, it must be broken off to allow a clear depth 

 of 4 inches of broken stone. 



The telfording shall then be rolled with a steam roller, all depressions 

 filled with stone chips or spalls, rolled and left true and even and 4 

 inches below the finished grade and cross-section. If a drain is to be 

 put in, it must be finished after the excavation is made and before the 

 gravel is spread. 



Drains. Where telfording is used, or where ground water from aside 

 hill may work injury to the road, you will build drains. 



If the road passes through a cut, you will place a drain on each side. 



If the road is on a side hill, you will place a drain on the up-hill 

 side only. 



All drains must be carried to a proper outlet, either to a culvert, to 

 another drain or through the bank. 



