116 
Steel ties, however, have come seriously into competition only since 
the increase of mild-steel production. This material is less liable to 
breakage than ordinary steel and less injured in punchiug the holes for 
fastening. A steel is used with a tensile strength of 25.4 to 28.6 tons 
per square inch, and a minimum contraction of 30 to 40 per cent.* 
SHAPE. 
The great number of forms of metal ties and the modes of fixing the 
rail to the same must be puzzling to an engineer who has to select one 
of them. The simpler the plan the better. If equal safety is to be ob- 
tained, the metal tie must be of equal size and cover as much surface of 
the ballast as the wooden tie. Yet the amount of bearing surface ot 
the tie on the ballast, provided this be of good quality and incompress- 
ible, is of less importance than that the pressure exerted by the ballast 
on the underlying soil, which is often compressible, be distributed over 
the largest surface possible. It is not necessary that the ties have a 
large bearing surface on the ballast, nor that they be flat on their un- 
derside, but only that there be sufficient width between the outeredges. 
To meet the requirements of a good tie, which with the smallest 
amount of material possesses the greatest possible strength, affords a 
rational distribution of the pressure on the road- bed, and lies solidly in 
the road-bed, the profile is of great importance. 
The form adopted by the Prussian Railway seems to answer well these 
requirements. It is a box, with the addition of broad flanges at right 
angles to the sides of the box, at the end of which two short feet permit 
a secure hold in the bed material. A cross-section presents about this 
shape : 
no 
25()mm 
Many different patterns are in use, like the Vautherin, Elberfeld, 
Prussian, Rhenish, Austrian, and Webb's ties, on the London and 
Northwestern Railroad, with a chair for bull-head rail. 
Recent improvements in rolling machinery allow the making of ties 
of varying thickness and having the l-in-20 slope for the rail made in 
the process of rolling. 
By this a saving of 12 to 21 per cent, and a distribution of material 
to points where most required is possible. The minimum cross-section 
is kept for about two-thirds of the length, while under the rail and for 
a short distance on each side of it, it is thickened. 
The Netherlands State Railway, after many tests under various con- 
ditions, sharp curves and gradients, with iron and steel ties of various 
designs, and after carefully comparing cost of maintenance with that of 
* See note on jointed cross-ties, p. 125. 
