THE STEAM-ENGINE. 121 



the engine), no great difficulties arose. But looking on this 

 beautiful model of a six-column engine (familiarly known as 

 a " bed-post engine "), the favourite type of some thirty 

 years ago for factory purposes, you will see that such a ma- 

 chine, when subjected to rapid alternations of strain, due to 

 the use of high-pressure steam and of great expansion (on 

 which important points I hope to address you in my next 

 lecture), would be little competent to bear such strains j for 

 a machine to support them must have its parts well tied to- 

 gether, and our American friends, in the beam engines which 

 they have used with so much success in river steamers, have 

 appreciated this fact, and therefore instead of a " bed-post " 

 frame support of this kind, their walking beam, as they call it, 

 is generally at the apex of a triangular structure of very great 

 strength and of large base, but nevertheless even the American 

 frames are very cumbrous, and one can see how desirable it is 

 to arrive at a more simple form of engine. Notwithstanding 

 this desirability, the beam remained, and when we came to 

 paddle-engines we still used the beam, although we inverted it. 

 I have here a model which is really of historical interest, lent 

 by Messrs. Maudslay, of the engines of the " Great Western," 

 the first paddle steamer built for the purpose of crossing the 

 Atlantic, though I do not say it was the first which actually 

 crossed it. Here is the model of the inverted beam engine of 

 forty years ago, and I am sorry to say that the engineers of those 

 days cared more that the framing should accurately represent a 

 gothic window or an Egyptian temple, or some other piece of 

 architecture, than that it should be designed to resist the strains 

 which came upon it, and as a fact, they made an elaborately 

 ornamental but weak frame which had to depend on the 

 strength of enormous keelson, in the bottom of the ship to 

 keep the parts of the engine themselves in position. Notwith- 

 standing the strength of the keelsons, one frequently found the 

 frames broken and patched with wrought iron. 



By slow degrees we have, however, come to the direct- 

 acting engine the Bull engine, which I have shown you, is an 

 early example of it. Then we had some forty years ago or more 

 the horizontal engine, made by Taylor and Martineau, that 

 type of engine which is now probably more commonly used 

 than any other. Then we had by the elder Brunei an engine 

 with the two cylinders inclined at an angle of 45 degrees each 

 to the horizon, and by their connecting rods laying hold of 



