115 
It* 1 1n* greatest side strain of 7,350 kilograms (Hi, 000 pounds; ue exerted on tbo tail 
just ovcri he tic, and if two spikes arc used outside and one inside tor fastening, then 
if t lit' coefficient of friction between metal and wood bo u = ^, the two outside spikes 
must offer resistance R =7,350—^^^=4,350 kilograms (9,570 pounds), while under 
usual conditions thej cannot oiler more than 3,200 kilograms (7,040 pounds) ; one 
shock, therefore, is capable of loosening the rail here. Only when the three spikes 
are united by bed-plates does their resistance grow to 4,800 kilograms (10,560 pounds), 
or their total combined resistance to 4,800-f-:>,000 = 7,800 kilograms (17,100 pounds), 
against a strain of 7,:>50 (10,000 pounds). But this resistance is found only in abso- 
lutely sound ties. Still less secure is the usual mode of fastening against tilting; for 
the inside spike cannot offer more than 2, 050 kilograms' (4,510 pounds) resistance, 
while the attacking force may reach a maximum of 4,800 kilograms (10,00*2 pounds). 
D. — Comparison of long- and cross-tie systems. 
The former, if perfect, like all superstructures with single supports, is superior in 
regard to an even uniform transmission of the forco waves which form under the 
moving loads. The many supports of a cross-tie system exert a disturbing influence 
on this wave movement, in consequence of which the rail is not uniformly utilized. 
Therefore, iu any cross-tie system, rails must wear unevenly. 
It follows that on long-tie systems, smoother rolling of cars, and less wear of all 
parts, must result than on cross-ties; yet it is possible to get sufficient satisfaction in 
this respect from the latter system. 
Of more importance is the greater security of long- than cross-tie systems against side 
strains and consequent breakage of rails 
By use of bed-plates on each tie or enlargement of rail foot this objection can be 
overcome. 
In regard to drainage no satisfaction has as yet been obtained in the long-tie systems. 
The quantity of bed material needed amounts to the same in both systems. Replace- 
ment is probably cheaper with cross-ties. Metal weight is alike, yet in long ties the 
wearing parts are the lightest. 
The author concludes that, as only two points are in favor of the long- 
tie system, which can partly be attained in cross-tie systems, the latter 
will remain the standard. 
MATERIAL. 
Although steel is preferable to iron for surfaces liable to wear, like 
those of rails aud tires, yet it presents drawbacks in the case of parts 
subject to deflection only, as bridges and ties, and being brittle in winter, 
requires special precautions while cooling after leaving the rolls. 
The strength of an iron tie should be much greater than a wooden 
one, because the former must offer sufficient resistance to deflection 
over its whole surface, however well it may be packed, as the reactions 
of the ballast during the passage of trains are distributed uniformly 
over the whole of the packed portion. 
The faults in construction of iron ties were eliminated in those made 
of steel, which are not liable to split and break, as are the iron ties. 
The first trials with hard-steel sleepers were not encouraging. Yet 
some companies have laid test lines, inspected them carefully, and have 
kept records as to cost of maintenance (especially in Germany and 
Holland), and from these trials are derived the results and experience 
now available in regard to this material. 
