30 Mr Adamson on Rail-Roads. 



slight oscillatory motions, to which the machine must always be 

 liable, may be employed to keep the safety-valves from becom- 

 ing fastened or rusted in their sockets. 



For this purpose, it is only necessary to detach the valve from 

 the lever, upon which the principal compressing weight is hung, 

 and giving it the shape of a ball resting in a socket, to attach to 

 it a considerable weight, hanging like a pendulum inside the 

 boiler. This interior weight may also be so disposed as to give 

 intimation of over-feeding with water, as the fluid, when it 

 reaches the weight, will buoy it up, and help to open the valve. 

 The method of conveying the heat through the boiler in a longi- 

 tudinal tube, completely surrounded by the water, appears best 

 fitted for deriving from the fuel all the advantage it can afford. 

 A cylindrical tube has hitherto been used in the locomotive en- 

 gine ; but there are other forms which would expose more sur- 

 face to the action of the flame, with equal security against the 

 pressure within. Probably this pressure may even be convert- 

 ed into the means of safety. If the tube were elliptical, and 

 on that account ready to yield in one direction sooner than ano- 

 ther, this yielding may be employed to pull open a valve, and 

 allow the steam to escape, when the pressure approaches to any 

 dangerous intensity. The whole apparatus of the engine is sus- 

 ceptible of numberless different forms ; and it is not too much 

 to expect, that the mechanical knowledge and ingenuity of our 

 countrymen will lead them to many more perfect than those yet in 

 use. As far as I know, none has yet worked so advantageously 

 as those constructed according to the patent of Messrs Stephen- 

 son and Losh, Newcastle-upon-Tyne, and employed at the col- 

 leries of Killingworth and Hetton, in that neighbourhood. 



The estimates of the expence of the employment of steam 

 power upon rail-roads, do not seem in its favour, when com- 

 pared with horses moving at the velocity most favourable to 

 them, provided the cost of coals continues to bear the same ratio 

 to the expence of supporting horses as it does at present in those 

 districts of the kingdom where such constructions are likely to be 

 advantageous. Where coals are 10s. per ton, the total expence 

 per annum of a locomotive engine, including allowance for wear 

 and tear, and interest on its value, will be L. 330 ; the work 



done will, if estimated by their performance at Killingworth, be 

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