118 LECTURES TO SCIENCE TEACHERS. 



the Institution of Mechanical Engineers, is shown in the 

 Exhibition. It is a rail which, as you know, was provided 

 with teeth projecting from one side of it, into which cogs made 

 in a deep flanche of the bearing-wheel took, so as to ensure that 

 that wheel should move the train and engine and should not 

 slip upon the rail. In Blenkinsop's time this was thought to 

 be a necessity, and such rails were laid down to a considerable 

 extent. I find the sample rail has not been brought in, and 

 I therefore content myself by saying, that a piece of such 

 rail, which was for many years in actual use, is in the 

 collection. In the building also we have the original 

 Puffing Billy, the first engine which traversed, I believe, 

 for practical purposes, a smooth rail, and an engine which 

 worked from 1813 to 1862, and then was placed in its 

 honourable retirement to be revered by engineers. Alongside 

 of that we have Stephenson's "Socket." That engine is gene- 

 rally thought to be in the original condition in which it worked, 

 but a very cursory examination will show that is not so, and 

 those who have read last Saturday's Engineer will have seen 

 a criticism on that Exhibit, pointing out that there have been 

 material alterations, and that therefore it should not be looked 

 upon as showing the exact state in which the engine was put 

 to work in 1830. The other day when calling on Mr. George 

 Robert Stephenson, President of the Institution of Civil 

 Engineers, and now the representative of the Stephenson 

 family, I looked at a model in his possession of the " Rocket," 

 a model which had been made by a man who had driven the 

 engine for many years, and when I found there was doubt 

 cast upon the extent of the alterations, which the real engine 

 had suffered, I thought it would be well to get the model 

 here, and here it is on the table. There is no doubt what- 

 ever that this model corroborates the statement in the 

 Engineer, and shows you really the engine as it worked in 

 1830, without the alterations which have been made in the 

 actual engine now deposited. The alterations, although rather 

 numerous, were not important. In the original engine, as 

 shown in the model, the cylinders were at a considerable 

 angle. You will find that in the real engine they lie at a 

 much less angle. In this model also there is no smoke box, 

 and in the engine there is. I do not know that there are any 

 really important points of difference, but nevertheless when 

 a thing is exhibited for its historical interest, it is as well you 



