324 Mr D. Stevenson's Remarks on the 



Fig. 1. On examining these blocks, I found many of them 

 split, caused no doubt by undue pressure, arising from the dif- 

 ficulty of procuring a solid bed for so large a stone. Mr Vig- 

 noles, it is believed, has recommended their removal, and the 

 substitution of the common insulated block. The object in 

 adopting this sort of block was to form a road as perfectly rigid 

 or inflexible as possible. It is also useful in preventing the rails 

 from being separated, which, especially on sharp curves, is apt 

 to take place. This connection between the rails on the New- 

 castle and Carlisle Railway is formed by means of a bar of malle- 

 able iron, with a cheek formed at both ends as a seat for the 

 rails, while the bar itself rests on the stone blocks, as shewn in 

 Plate IV. Fig. 2. In this way, the objections arising from the 

 expense of procuring large blocks of stone, and their liability to 

 break, are obviated. On the Dublin and Kingstown Railway, they 

 are much troubled by the tendency which the chairs have to shake 

 loose from the granite blocks ; to counteract which, the use of 

 felt, wood, lead and copper, has been applied as a bedding for 

 the chair, but with little effect. The rails of the Liverpool and 

 Manchester line are more easily kept in repair ; here, freestone 

 blocks, measuring two feet square, are used for supporting the 

 rails, but the mode of fixing these to the chairs is more simple 

 than in the Dublin and Kingstown Railway.. The method, how- 

 ever, of fixing the chairs to the blocks is the same in both cases. 

 The difficulty experienced in keeping the Dublin and Kingstown 

 Railway in repair may arise in a great measure from the rigi- 

 dity of the rails, produced by the unyielding nature of the gra- 

 nite blocks. Between Liverpool and Manchester, the part of 

 the road requiring least repair is that over Chatt Moss, where 

 the railway may be said to float on the surface of the bog. 

 The motion of the trains in passing over this part of the line 

 is also sensibly retarded. The weight of the train causes a de- 

 pression or hollow in the road, which offers the same resistance 

 as a gentle inclined plane, to the progress of the engine. This 

 is a good practical proof that a flexible railway offers more resist- 

 ance to the motion of a carriage passing along its surface than 

 one which is in a more rigid state, while it possesses the advan- 

 tage of being much more easily kept in good repair. 



When the curves on this line of railway are of small radius, 



2 



