42 THE HISTORY OF [SECT. i. 



a simple and portable engine for cases where water was scarce, or where gaining 

 the whole effect of the fuel was of less consequence than moving a cumbrous 

 load. 



Indeed their high pressure engines were intended chiefly for propelling 

 carriages upon rail-roads ; and when used for this purpose the boiler was composed 

 of cast iron, of a cylindrical form, mounted horizontally upon a frame with four 

 wheels, the cylinder of the engine being placed vertically within the boiler near 

 to one end. The piston rod moved a cross head, between two guides ; and by 

 a connecting rod descending from each end of the cross head to two cranks, the 

 motion was communicated to the wheels of a carriage : a fly wheel in this case is 

 not required, because the momentum of the carriage supplies its place. 1 



The first trial of this species of moving power for carriages took place on a 

 railway at Merthyr Tidvil in 1805. Its use was not at that period followed up, 

 but it is now with some slight modifications extensively employed on rail-roads. 



Several projects for trifling variations in the construction of engines, and for 

 methods of applying fuel, appeared about this time, but none of either sufficient 

 novelty or importance to claim particular attention. 



The nature and application of heat had been so well illustrated by Rumford, 

 and many of its more recondite properties so ably developed by Leslie, that there 

 seemed to be little reason to expect any material improvement beyond the best 

 mode then in practice. The cylindrical boilers which Blakey projected, and Rum- 

 ford had tried, were again remodelled by Woolf ; but in his practice we find he 

 has reverted to methods nearly like those of Rumford, instead of continuing to 

 follow his own. The steam engine itself had also apparently obtained its most 

 simple and efficient form, except in the eyes of those who expected to use its direct 

 rotary action. The fact however was otherwise, for by a most simple change of 

 a previous combination it had to be materially improved. 



1804. AUTHUR WOOLF. 



57. The mode of condensation invented by Watt being now public property, and 

 the term of Hornblower's patent having expired, Mr. Woolf adopted the arrange- 

 ment of the latter, with the alteration of using high pressure steam in the small 

 cylinder, and employing the condensing apparatus of Watt. But a change of the 

 working force of the steam would have been too slight a ground to have claimed 

 a patent upon, and therefore he commences his specification with a claim of the 



1 It is but justice to observe, that Mr. Murdock made his working model of a locomotive engine 

 in 1782, and that, as Mr. Trevithick was a pupil of Murdock's, then in Cornwall, it is natural to 

 suppose that he received many of his ideas of locomotion from that gentleman. 



