286 PRACTICAL ARBORICULTURE 
QUALITY ESSENTIALS FOR RAILWAY SLEEPERS. 
Railway officials and investors are now giving much attention to the 
subject of suitable materials available for cross-ties or sleepers, whether, they 
shall be made of metal, concrete, or a combination of several materials, or 
of wood, and if the latter, what species of trees are best adapted for the pur- 
pose, and which kinds may be grown within the limit of time when the present 
supply shall have become exhausted. These are subjects to which attention is now 
riveted. 
There is a great danger in going to extremes with various tests, and in 
placing too great stress upon immaterial points, and thus losing sight of the 
more essential qualities. 
We desire to point out some prominent features which should receive 
consideration by engineers, in forming a scale of tests, and we place these 
in the following order: 
(1) Durability. 
(2) Elasticity. 
(3) Transverse strength. 
(4) Cost of production. 
(5) Time required for production. 
(6) Spike-holding quality, or density. 
DURABILITY. 
In considering the qualification of metals it should not be overlocked 
that oxidization, electrolysis, danger from breakage, especially under frost 
conditions, tend to reduce the value and longevity of sleepers, while in the 
use of cement concrete and combinations in which this material is used, the 
effect of frost and impact of heavy trains and of disintegration must be kept 
in view. 
In the use of wooden sleepers, the experience of railway officials, actual 
long-term trials by many railways, and the credible statements of those who 
have had long and practical experience in the use of certain woods, are 
entitled to large consideration. 
In the chemical treatment of inferior woods, the cost of impregnation 
and of transportation to and from the plant must be considered together 
and if a timber possesses equal or greater durability without the necessity 
for such artificial chemical treatment, it should receive due credit for this 
valuable quality. 
