492 ROBERT STEPHENSON'S NARRATIVE. APPENDIX. 



you practically be always applying a power in excess of the 

 resistance, a constant increase of velocity would of necessity 

 follow without any limit. This is so obvious to most professional 

 men of the present day and is now so axiomatic, that I only 

 allude to the discussion which took place when these experi- 

 ments of my father were announced, for the purpose of showing 

 how small was the amount of science at that time blended with 

 engineering practice. A few years afterwards, an excellent 

 pamphlet was published by Mr. Silvester on this question ; he 

 took up the whole subject and demonstrated in a very simple 

 and beautiful manner the correctness of all the views at which 

 my father had arrived by his course of experiments. 



" The other resistances to which carriages were exposed were 

 also investigated experimentally by my father. He perceived 

 that these resistances were mainly three : the first being upon 

 the axles of the carriage ; the second, which may be called the 

 rolling resistance, being between the circumference of the wheel 

 and the surface of the rail ; and the third being the resistance of 

 gravity. 



" The amount of friction and gravity he accurately ascertained ; 

 but the rolling resistance was a matter of greater difficulty, for 

 it was subject to great variation. He, however, satisfied himself 

 that it was so great, when the surface presented to the wheel 

 was of a rough character, that the idea of working steam- 

 carriages economically on common roads was out of the question. 

 Even so early as the period alluded to he brought his theoretical 

 calculations to a practical test ; he scattered sand upon the rails 

 when an engine was running, and found that a small quantity 

 was quite sufficient to retard and even stop the most powerful 

 locomotive engine that he had at that time made. And he 

 never failed to urge this conclusive experiment upon the 

 attention of those who were wasting their money and time upon 

 the vain attempt to apply steam to common roads. 



<: The following were the principal arguments which influenced 

 his mind to work out the use of the locomotive in a directly 

 opposite course to that pursued by a number of ingenious 

 inventors, who between 1820 and 1836 were engaged in 

 attempting to apply steam-power to turnpike roads. Having 

 ascertained that resistance might be taken as represented by 

 10 Ibs. to a ton weight on a level railway, it became obvious to 

 him that so small a rise as 1 in 100 would diminish the useful 

 effort of a locomotive by upwards of fifty per cent. This fact 



