1897.] NEW YORK ACADEMY OF SCIENCES. 147 



of the heavier wheel loads as distributed by the stiffer rails 

 through the tie to the ballast and roadbed, are less than was the 

 combined static and dynamic effects of the lighter wheel loads 

 as distributed by the lighter rails through the tie to the ballast 

 and roadbed. The generation of an unnecessary and destruc- 

 tive force has been 2^r evented. 



Every tie underneath the lighter rails received its load more 

 in the nature of a suddenly applied blow than a gradually applied 

 load, and its abrasion under the rails was very rapid. 



As the cost of ties is now much greater than the cost of rails 

 for renewals, the saving in expense for ties will be quite an 

 item in paying for the stiffer rails. Treated ties can be now 

 used under the stiffer rails, since the abrasion has been so much 

 reduced. 



There is considerable discussion as to whether the freight 

 car loads should be reduced or increased. I find the tendency 

 in the latter direction, as a number of cars of 80,000 pounds 

 capacit}'^ are in use and others are building for loads of 

 100,000 pounds. 



The freight car wheel load is now an international commercial 

 matter and beyond the control of an}'- one railroad company, 

 just as is the freight rate per ton, but what is largely under 

 the control of the company over whose lines the cars pass is 

 whether the dynamic effect of the wheel loads shall be but a 

 slight increase over the static load, or 50 to 100 per cent, greater 

 to be transmitted to the ties, ballast, and roadbed, increasing the 

 cost of transportation and maintenance of the equipment and 

 permanent way. 



One of tbe great objects to be obtained in permanent-way con- 

 struction is to prevent the dynamic effects of the moving wheel 

 loads of either the locomotives or cars from reaching much 

 magnitude, for the effects of the static loads combined with the 

 dynamic effects, when finally distributed to the roadbed, should 

 always be less than its elasticit}^ ; otherwise the track cannot 

 acquire any high degree of stability, nor be most economicall 

 maintained. 



The 80 and 100-pound rails are double and treble the stiffness 

 of the former four and one-half, 65-pound rails, with much wider 

 bearing surface for the wheels, and, as would be expected, the 

 diagrams show that the waves of pressure from the wheel loads 

 must be distributed over a much greater area of the roadbed, 

 reducing their intensity to an amount more easily carried by the 

 elasticity of the roadbed. The elasticity of the roadbed, though 

 a very limited quantity, is a fundamental principle of main- 

 tenance of way, but it has received too little specific attention, 



