MECHANICS AND USEFUL ARTS. 51 



with the side flue ; it is fixed just below the water level in the boiler, but 

 may be fixed at any elevation, or in any position requisite, and can be 

 applied to any kind of boiler, as an opening into a side or centre flue is all 

 that is required. The pipe is perforated with a number of holes, half an inch 

 in diameter, so placed as to be subject to the immediate action of the furnace 

 fire. In these holes are metal plugs, more or less fusible, according to the 

 working pressure of the boiler. The moment the water in the boiler, from 

 neglect or otherwise, is below the level and leaves this pipe bare, the heat 

 from the furnace acts upon the plugs, which melt, and the steam, oozing 

 through the holes, immediately relieves the pressure in the boiler and ex- 

 tinguishes the fire, thus preventing the possibility of an explosion. 



Smoke Consumer for Steam Boilers. Mr. J. L. Jeffree has secured a patent 

 in England for placing at the back of the fire-box of tubular marine boilers 

 hollow flattened pipes, which communicate, through air flues, with the 

 atmosphere. These tubes become hot and heat the air which flows in to 

 mix with the smoke from the fires, thus supplying it with sufficient oxygen 

 to promote perfect combustion and consume the smoke. It is applicable only 

 to steamers using bituminous coal. 



Prevention of Boiler Incrustations. An invention by Thomas Sloan, of St. 

 Louis, consists in providing a tank or vessel, the upper part of which is hi free 

 communication with the steam space of the boiler, and the lower part with 

 the water space thereof. The vessel is furnished with a certain arrangement 

 of pipes and other appliances, by which the feed water is introduced near the 

 top of the said vessel, and caused to descend in a thin sheet through the 

 steam space. During this transit through the steam, the water becomes 

 heated to 212, at which temperature the mud and other impurities separate 

 and fall to the bottom of the vessel, which is cooler, and there remain, while 

 the purer water above is fed into the boiler. The purifying tank may be 

 cleaned of its deposits without trouble, as often as required. "We are 

 informed that this invention renders Mississippi river water so pure, before it 

 reaches the boiler, that scarcely any trouble is experienced from incrustation. 

 Scientific American. 



PRESSURE OF STEA^I IX BOILERS. 



A pamphlet has been published in England, by Mr. Anderson, the well 

 known machinist, on the management of steam boilers, in which he says that 

 the pressure within a boiler is greater than is generally supposed. With a 

 pressure of 50 pounds per square inch, it amounts to 7200 pounds on every 

 part of the surface exposed to the steam, amounting frequently to many 

 thousands of tons in the boiler, thus accounting for the enormous havoc made 

 by explosions. The joints are weaker than the solid parts ; good solid plate 

 will withstand from 56,000 to 60,000 pounds per square inch of sectional 

 area the joints will give way at about 34,000 pounds, which shows the 

 importance of seeing that the rivets and other fastenings are always in sound 

 condition. Mr. Anderson divides explosions into four classes, viz. from want 

 of strength, deficiency of water, heating of plates, and the variety of other 

 circumstances. 



