S4 Transactions. — Miscellaneous. 



Don-condnctor. To prevent a circulation of cold air from end to end of the 

 boiler, I attached a piece of sheet-iron, cut to the ciix-umference of the boiler, 

 to the ends of the battens on the grids at each end of the boiler G (Fig. 1). 

 A coat of paint on the canvas com])leted the appai-ifcus. 



I exhibit a full-size section of one of the grids, 'U'ith felt and canvas 

 attached, to be placed for reference in the Museum of the Society at 

 Auckland. I have attached the felt to the grid in this section to show the 

 apparatus complete ; but, in practice, the felt and canvas only are attached to 

 each other, but not to the grid, so that each can be stripped from the boiler 

 without difficulty. 



I come now to results. I find that loss by radiation and condensation is 

 reduced to a minimum ; the canvas covering of the boiler being always quite 

 cool, with, steam at 5Clbs. As an instance, I may mention that when the 

 engines stop at 6 o'clock p.m., with steam at 501bs., with the felt on, at G o'clock 

 next morning steam is about 251bs. ; without the felt, steam goes down to nil 

 before G o'clock next morning, the dampers being in both cases the same. The 

 saving of coal has, of course, been considerable. Nine months have elapsed 

 since I applied this mode of felting at my own works, and I find that both, 

 wood and felt are jiractically uninjured. 



Where compound engines are in use, this mode of felting the steam pipes 

 leading from the boilers to the high-pressure engine, and from the high- 

 pressure to the condensing cylinder, will be found most effectual in preventing 

 loss by condensation or radiation, besides being comparatively indestructible. 

 For covering steam domes and engine cylinders it is equally effective. For 

 these latter the grids and felt may be covered with wooden battens, hooped 

 and varnished as usual. 



It will be necessary to observe, when coveiing pipes or other steam 

 chambers of small diameter, that the cranked pieces of hoop-iron must bo 

 placed sufficiently near to each other to secure a space of 3 in. or 4 in. between 

 the steam-pipe and felt. In all cases it will be found moi'e practicable to run 

 the pieces of plane hoop-iron round the pipes or cylinders to be covered, 

 running the cranked pieces longitudinally, as already described in the case of 

 steam boilers. 



