THE CONQUEST OF TIME AND SPACE 



board was made "not a single professional man of 

 eminence could be found who preferred the locomo- 

 tive over the fixed engine, George Stephenson only 

 excepted." But with the glaring defects of the cable 

 road, and the enormous cost of maintenance impressed 

 upon the directors, the idea of the locomotive became 

 at once more attractive, and the performance of Ste- 

 phenson's locomotive was more carefully investigated. 

 The upshot of these investigations was the offer of a 

 prize of £soo for a locomotive that, on a certain day 

 would perform certain duties named under the eight 

 following headings: — 



1. The engine must effectually consume its own 

 smoke. 



2. The engine, if of six tons' weight, must be able 

 to draw, day by day, twenty tons' weight, including the 

 tender, and water-tank, at ten miles an hour, with a 

 pressure of steam upon the boiler not exceeding fifty 

 pounds to the square inch. 



3. The boiler must have two safety-valves, neither 

 of which must be fastened down, and one of them 

 completely out of the control of the engineer. 



4. The engine and boiler must be supported upon 

 springs and rest on six wheels, the height of the whole 

 not exceeding fifteen feet to the top of the chimney. 



5. The engine with water must not weigh more 

 than six tons, but an engine of less weight would be 

 preferred although drawing a proportionately less load 

 behind it ; if of only four and one-half tons it might be 

 put on four wheels. 



6. A mercurial gauge must be affixed to the machine. 



