PRACTICAL ARBORICULTURE 287 
ELASTICITY. 
Every railway frog in the world is a practical illustration of the neces- 
sity for elasticity in rail connections with the bed-plate or sleepers. Here 
rigidity is the positive rule. Steel rails are bolted to steel connections, and 
these require frequent repairs and renewals. The same result must be 
expected whenever this policy of rigidity governs cross-tie connections. The 
safety of swiftly moving trains, especially under American railway conditions, 
depends upon this element of elasticity which exists in wooden ties, every 
spike being bedded in a cushion of compressed wood fibers, and each tle 
being an elastic bed-plate. 
TRANSVERSE STRENGTH 
of wooden sleepers is an important consideration, for the bearing is  fre- 
quently more substantial in the center than at the ends of the timber, 
and often oak ties are broken from this cause. It is probably true 
that knotty, cross-grained and brash timbers are the ones which thus 
give way. In making comparative tests, with white oak as a standard, 
it should be remembered that the best grade of oak has not been used for ties 
for many years; it would be much too costly for this purpose. A sleeper 
containing 45 feet b. m. would at $60 per 1,000 feet, its value for furniture 
manufacture, cost $2.70, or five times the average price of ties on our American 
tracks. 
It is not fair, therefore, to test catalpa, or other woods which may be 
grown specially for use as sleepers, with white oak of a much higher grade 
than is used in the track for sleepers. 
Cross ties are never suspended at the two ends, having to support the 
weight of a train in their center, and it is not proper to demand of any 
timber a far greater strain than could ever be required of it. Enough is 
sutficient. 
COST OF PRODUCTION. 
Perhaps the average price of standard railway sleepers in the United 
States may be sixty cents each, although the range is from thirty cents for 
inferior to seventy-five cents, depending upon the competition among pur- 
chasing lines and distance of haul. 
In considering timber culture for the production of ties, early maturity 
of trees is an important factor, the cost of production being largely governed 
by the time required to grow the wood, during which period interest, taxes 
and expense of maintenance are accumulating. 
In portions of Europe, Asia and Africa, where wood is scarce, many 
sleepers are imported from America, the expense of transportation by sea, 
transfer at two docks, and freightage to points where required, is very large, 
so that metal sleepers are in close competition with wood. If to this expense 
for wooden ties there is added the cost of chemical impregnation, the cost 
may even exceed, in some localities, that of metal sleepers. 
