PeOCEEDINGS of the rOLYTECUXIC ASSOCIATION. 1019 



tiv:ax and depositing tLcni in the mnd-drura, whence they are hlown 

 ont. 



Economy of Fuel. 

 Tliis resnlts from perfect coinhustion and thor(ni^-h absoi-ption of 

 the heat. The products of conjbustion i)ass readily through the wide 

 interstices l)etween tlie tul)es into tlie combustion clnuuber, where 

 tliey mingle and complete the combustion commenced in the furnace, 

 thence passing twice lietAveen the staggered rows of tubes, the avail- 

 able heat is thoroughly extracted. This ari-angement of the tubes 

 l>reaks up the current of gases and causes them to impinge upon and 

 wra|) around the tubes, whereby the whole surface is made availalde. ■ 

 The experiments of Dr. Alban, and of the U. S. Navy, have proved 

 that a given surfice arranged in that manner is thirty per cent more 

 efficacious than when in. the form of lire tubes as usually employed. 

 The rapid circulation of the water also assists materially in the e-xtrac- 

 tion of the he;it from the gases, not onl}' by the presentation of fresh 

 water continmdly, but also by the prevention of incrustation. 



Dky Stea:m. 

 Tlie rapid circulation of the water in a continuous circuit, in con- 

 nection with the large disengaging snrfice in the steam and water 

 drum, causes a thorough se}>aration of the steam from the v\'ater, and 

 preveiits what is kn.owii as "■' pi'iming"' or ''foaming,'"' the steam pass- 

 ing away from the boiler dry even when the boiler is f ji'ced to its 

 utmost capacity. 



Accessibility. 

 A hand hole at the end of each tube permits access thereto for 

 cleaning should tliey become scaled by the use of very bad water, and 

 manholes in the steam drum admit access to that part, for the same 

 purpose, 'should it be neces>;iry, f )r any cause, a tu])C nuiy bo readily 

 removed and another substituted. Bonnets at either end of the mud- 

 drum also permit access thereto fjr cleaning. 



Safety from Explosion. 

 It is now fully estaldished by tlie experience of boiler insurance 

 associations in this country and England, that all the mystery of boiler 

 explosions consists in a want of suiticient strength to withstand the 

 pressure. This lack of strength may 1)0 inherent in the original con- 

 struction, but is most coinmonly tlie effect of weakening of the iron 



