Mr Adamson on RaitRoads. S9 



rJience, 



5 1+50 sin i 



7n' = TT X r 



3 " 1 + 15 sin i ' 

 which is the same equation as before, when sin i = 0. When 

 sin i z= gV, then m' — 3.125; in which case, the power of the 

 locomotive engine ceases, and the resistance of the rope becomes 

 equal to the whole strain placed upon it. This must be consi- 

 dered as, on those conditions, the hmit of the length of a stage 

 between two fixed engines, and since a chain of short links, of 

 the same strength as a rope, would be heavier, and would re- 

 .quire heavier rollers, but would not acquire so great an excess 

 of strength, to compensate for its wasting, the substitution of it 

 would probably make no great change on the results. 



It appears, then, that if a Hne of road were xvorked by fixed 

 engines, the number must be very great ; and though certainly 

 the expenditure of power, on a given conveyance, may be ren- 

 dered less than is required by locomotive engines, provided the 

 distances between the stations be less than those determined by 

 the preceding rules, yet, when we consider the many inconve- 

 niences to which the employment of them subjects us, we must 

 conclude that they should be resorted to only when other means 

 are inapplicable. They possess no pecuhar advantages, as to 

 safety, to counterbalance those defects ; any danger arising from 

 liabihty in the carriages to be overturned, or from swiftness of 

 motion, should the machinery be suddenly stopped, will be the 

 same in both cases, or will be increased by the employment of 

 fixed engines. Carriages containing any persons, or any pro- 

 perty easily injured, may be kept at a safe distance from a 

 travelling engine, so as to be unendangered by its casualties, 

 and easily brought to rest, before reaching it ; but would be ex- 

 posed to a dangerous concussion by a pause in the macliinery 

 of the fixed engine. The locomotive engines must certainly be 

 high pressure-engines, but, from their size and treatment, are far 

 more likely to be deficient in the power of generating steam, than 

 able to spare any for explosions. There are circumstances, also, 

 which render the employment of the high pressure-engine less 

 dangerous in this form than in other cases. The distance at 

 which it may be made to act, will render injury very improl 

 bable to all, except those in immediate attendance on it; and the 



