Mr David Stevenson''s Observations on the 



rivetting or fixing the tubes. In this view, letter I represents 

 the end plate of the boiler, m the end of one of the brass tubes, 

 and w is a steel ring, about one-eighth of an inch in thickness, one 

 inch in breadth, and slightly tapered. This ring is driven into 

 the brass tube, after it is fitted into the boiler plate, by which 

 means the tube is wedged against the plate, and thereby ren- 

 dered water and steam tight. The tubes are proved by means 

 of a water pressure of 50 lb. on the square inch, and, notwith- 

 standing this, they frequently burst. When this accident hap- 

 pens, the engineer stops both ends of the broken tube with 

 wooden plugsi The mechanics connected with the railway pre- 

 fer the large lubes of three inches bore to the small ones, which 

 are more apt to get choked with soot and ashes. The boilers 

 are generally seven feet long, and four feet in diameter, and con- 

 tain about seventy or eighty of the small-sized tubes. Round the 

 boiler there is a Zo^^M/^or casing of one half inch deal timber, fix- 

 ed with iron hoops, as shewn in Plate V., which being a non- 

 conductor, prevents the radiation of heat, and greatly facilitates 

 the generation of steam, especially in frost, or in a damp state of 

 the atmosphere. The time required for getting up the steam, 

 even in the most improved boilers, is generally above an hour, 

 when every thing is in a cold state.* The Act of Parliament, 

 in consequence of the smoke raised by pit coal, enforces the ex- 

 clusive use of coke, which increases the expense of fuel about 

 40 per cent. 



The cylinders are horizontal in all the locomotive carriages, 

 with the exception of two, in which they are vertical, and these 

 are not found to answer so well, and require more repair ; the 

 cause of which may be satisfactorily explained in the following 

 mantier : — When the cylinders are vertical, the machinery can- 

 not yield to the up-and-down motion of the piston rod, and has 

 consequently to bear the whole shock ; while, on the other hand, 

 when the cylinders are placed horizontally, the motion of the 

 piston tends to impel the carriage along the rails, by which the 

 shock is deadened, and has not so injurious an effect upon the 



• A member of the Society having mentioned, that on the Glasgow and 

 Garnkirk Railway, the steam is raised in twenty minutes, I think it neces- 

 sary to remark, that the time stated in the text is dated from the first ap- 

 plication of heat to the fuel, and is the result of many observations made by 

 me while at Liverpool. 



