62 BULLETIN" 724, IT. S. DEPARTMENT OF AGRICULTURE. 
under the supervision of the Bureau of Public Roads, showed a total 
average cost for crushing and quarrying of about $1.25 per cubic 
yard. The total quantity of crushed stone taken from the nine 
quarries was about 55,000 cubic yards. 
V-DRAIN FOUNDATIONS. 
The proper method of constructing V-drain foundations has already 
been discussed under " Drainage " on page 37. A typical cross sec- 
tion for such a foundation is shown in figure 13 and the ordinary 
method of construction is illustrated in Plate V. 
TELFORD FOUNDATIONS. 
The stone used in constructing Telford foundations should be 
sound and tough, so that when wedged into the foundation indi- 
vidual pieces of the stone will not crack or be loosened when rolled 
or when irregularities are broken off with a hammer. Since the 
relation between the different particles of stone composing a Tel- 
.ford foundation necessarily must be almost wholly mechanical and 
its rigidity, therefore, depend on the interlocking of slight irregu- 
larities in adjacent stone surfaces, it is evident that if the stone lacks 
in soundness or toughness, the individual particles might be loosened 
easily by the shearing off of these irregularities, and whatever load 
came upon stones so loosened would be transmitted almost undis- 
tributed, and therefore unreduced, to the subgrade. Such varieties 
of stone as soft limestone, brittle sandstone, and decayed granite 
could not, as a rule, be used satisfactorily in a Telford foundation, 
though, under favorable subgrade conditions, they might be used 
advantageously in a crushed-stone foundation. 
Satisfactory Telford foundations may be constructed of either 
quarried or field stone. But, in general, quarried stone is to be pre- 
ferred, not only because it usually is tougher and more durable, but 
because it is easier to obtain a good mechanical bond between fresh 
stone surfaces than between those which have been exposed to the 
weather for some time and worn more, or less smooth. It is also 
easier to secure a firm uniform bearing for pieces of stone having 
approximately plane surfaces, than where the surfaces are rounded, 
as is the case with field stone. 
The dimensions individual stones should have need not be fixed 
very definitely, except that the depth should be equal to the depth 
of the foundation. In general, the length should not be less than the 
depth nor greater than about twice the depth. If the length is less 
than the depth the stone will not be in a stable position, while if the 
length is greater than about twice the depth it is difficult to insure 
a uniform bearing. The minimum allowable width depends some- 
what on the quality of the stone used as well as on the dimen- 
sions. Where -an exceptionally hard and tough variety of stone is 
