100 
Changing conditions of weather, by repeated soaking and drying of 
the tie. inevitably indnee change of volume, and therefore alone make 
a sate fastening of the rails to a wooden tie problematic. 
To this add the also problematic capacity of the fastenings, whether 
spikes or bolts, to secure the rail. 
Further, there is to be considered the very unequal capacity of re- 
sistance which ties show, according nor only to the kind of timber, but 
to the locality from which they come. This difference of quality de- 
pends on a number of influences, such as the conditions of the soil on 
which the tree has grown, the age of the tree, as well as the season of 
its felling, and cannot be overcome by impregnation or otherwise. 
Quite different are the possibilities in this respect with iron or steel 
as material. 
The uneveuness of the track, produced by varied behavior of the 
i Les, works detrimentally also on the rails and on all parts of the road- 
bed, so that for safety as well as efficiency and ultimate economy alone 
the metal superstructure deserves consideration. 
From a railway poiut of view the introduction of metal ties recom- 
mends itself as affording additional revenue, if otherwise the cost of 
first construction and of maintenance is satisfactory, for the manufac- 
ture of a ton of steel ties creates a traffic over the railways of tico tons of 
ran- material. 
The first introduction of metal (then iron) ties dates back probably 
to the year lSGi, when the Brunswick railways in Germany laid test 
lengths of longitudinal iron stringers, so that an experience of over 
twenty years, valuable on some points at least, is afforded. The Dutch 
and Swiss companies followed soon with improvements in the system 
of construction, and the use of this substitute has been gradually ex- 
tended, so that now all the railroad companies of Holland have intro- 
duced metal ties on their lines. 
In order to make the first introduction of metal ties possible, it was 
necessary to make the initial cost of the longitudinal tie (Hilf system) 
as near that of the wooden structure as possible; consequently they 
were rolled unduly thin, the rail also was made weak, and thus break- 
ages were not uufrequent, creating distrust of the system. The at- 
tempt to remedy this by increasing the weight of ties from seventy- 
seven to one hundred and sixty-five pounds failed on account of the 
increased expense. The same fate attended the attempt to strengthen 
the tie by riveting or bolting to it plates for the rail to rest on, because 
of increased cost and less secure connection between rail and tie. 
Two systems of metal superstructure have been used in practice, the 
longitudinal and the cross-tie. 
The first metal ties were constructed upon the longitudinal system 
(Hartwich, Hilf, Scheffler), and even to-day, after nearly a quarter of a 
century of trial, opinions as to the superiority of one or the other sys- 
tem are wide apart, though latterly preference seems to favor the 
