incident to Steam Boilets. 



129 



meter, with ends of the same material generally of a hemi- 

 spherical form ; it is placed horizontally, the water occupymg 

 by far the larger portion of the space within, and the fire is ap- 

 plied under the bottom part. r. , , -, 



The section annexed shows the position of the boiler with 

 respect to the fire : the lengths which have been usually made 

 may be stated at from 20 to 40 feet, and the diameter from 4 

 to 5 feet. The plates generally employed for making these 

 boilers are §ths thick. 



This construction is common, I believe, in America, but 

 they were not much used in England until they were intro- 

 duced by Messrs. Taylor and Martineau, who have made 

 them in a very excellent manner ; and by placing the bar across 

 the centre, as shown in the drawing, and which is repeated at 

 intervals throughout the whole length, they have given them 

 the greatest strength, and rendered them easy to repair. I have 

 never heard of any one of these boilers having burst or caused 

 any disagreeable accident. 



In our mines in North Wales I have used them with great 

 advantage, and our agents and engineers prefer them to any 

 other, and find that they generate steam rapidly, and appa- 

 rently with occonomy; but, as there is no monthly report there 

 as in Cornwall, this point cannot be ascertained precisely. 



I expected the same advantage by using them in Cornwall, 

 with the further one of increased security. In this I have 

 been disappointed : the difference in the quality of the coal 

 appears to be the reason ;— in North Wales it is a free burning 

 and bituminous coal, and makes little or no clinker, and there- 

 fore essentially different from what I have described the coal 

 used in Cornwall to be. With the latter these boilers do not 

 appear to afford steam freely; whilst the brick sides of the fire- 

 JVcwSt-nVx. Vol. l.No.2. JVi. 1827. S place 



