64 BULLETIN" 724, U. S. DEPARTMENT ,0F AGRICULTURE. 
CONSTKUCTION. 
In constructing a Telford foundation the stones are set by hand on 
the prepared subgrade so as to break joints roughly in the courses, 
which should be approximately straight across the road. Each stone 
should be placed with its long dimension in the direction of the 
courses and should be bedded evenly on the subgrade. The stones 
should be set together as closely as practicable and should be wedged 
firmly in place by means of spalls as the setting proceeds. 
Ordinarily, the Telford stone is hauled out and distributed on the 
subgrade ahead of the men who do the setting, the individual pieces 
being of such size that they may be handled readily by one man. 
Then, as the stone is needed for use, it is broken to the required size 
with sledge hammers and placed in the foundation as above described. 
Under average conditions two laborers to each stone setter are re- 
quired to select and carry the stone to where it is needed, and to assist 
in wedging up the foundation with spalls. 
As the wedging proceeds all projections of more than about 1 inch 
above the intended surface of the foundation should be broken off 
with hammers and the spalls thus obtained used as wedges. When 
the laying and wedging are complete, the surface of the foundation 
should present a fairly uniform appearance and should be free from 
open or loose joints. 
As soon as practicable after the stone is placed the foundation 
should be rolled with a power roller weighing about 10 tons. If de- 
pressions develop under the roller that indicate failure of stone or soft 
subgrade, they should be corrected by taking up and relaying the 
affected portions, and the rolling and relaying should continue until 
no such depressions occur. If the road crust is such as to require a 
smooth foundation, the irregularities of the Telford may be over- 
come by spreading a layer of coarse sand or stone screening over the 
surface while the rolling is in progress. In the past, however, Tel- 
ford foundations usually have not been employed except in connection 
with macadam or gravel road crusts, and with these the small irregu- 
larities of the Telford surface are not objectionable. 
COST OF TELFOKD FOUNDATIONS. 
The cost of setting Telford varies with the character of stone used. 
Where the stone is laminated, for example, the individual pieces 
usually will be such as to fit snugly together and comparatively little 
wedging with spalls will be necessary. Thin-bedded limestone lays 
especially well in Telford construction. But if the stone is unstrati- 
fied, it will break into irregular pieces, and the work of breaking off 
projections and wedging up the foundation will be increased corre- 
spondingly. A study of available data shows that where the stone is 
