1000 TjiAysAcrioxs OF THE Americax Institute. 



Steam Boilers. 

 Mr. John A. Coluinan said that we are apt to get on side issues 

 before we liave got a plan. The steam boiler is a very important 

 article, and its form and management has always excited much dis- 

 cussion. In presenting the subject we should commence at the top 

 and go to the bottom. He would therefore take the top of the grate 

 bars as his first point. AVliat takes place when coal is shoveled on 

 the top of the grate ? The first thing is the separating of the carbon 

 from the hydrogen of the coal, and this cannot be done unless the 

 coal is given a sufficient amount of oxygen, and generally when the 

 resulting gases are evolved from the coal, tliey have to ascend soma, 

 forty feet through the chimney. And, even if the proper amount of 

 oxygen is supplied, there is not sufficient time given for the proper 

 evolution of the heat. We must have a large combustion chamber. 

 In other words, slow combustion is the economical way to use coal. 

 It is not always practical to make heat by the various plans attempted. 

 There are many ways of making a furnace. A boiler with a water 

 leg is, on principle, defective. Boilers for marine purposes involrea 

 different set of principles from those on land. Therefore, that boiler 

 should be left to itself. The gases-, when evolved from the coal, are 

 \ery attenuated, and tliey go along unmixed with the coal ; 

 and chemists may take these gases and find dollars in them. If 

 molasses is poured on water, it will be difficult to get the two united, 

 but if a little molasses and water is first mixed and then put into 

 water the union will be made much quicker. Now, a steam-boiler is 

 nothing but a large kettle to boil water, and m'c want to know the- 

 best way to get the heat to the water in tliat boiler. A square foot 

 of iron will take so much time to heat it. The bottom of a pot is 

 the best form of boiler, and the nearer we approach to that will be 

 the best. The plain cylinder-boiler is as good a form of boiler as can 

 be made. A plain cjdinder-boiler in a cotton mill will furnish a yard 

 of cotton cloth just as cheap as the best tubular boiler. But they are 

 not generally used because they are exceedingl}^ dangerous ; and 

 being made long, contain in most instances, lukewarm water in some 

 parts. The results with tlie flue-boilers are no better than with the 

 cylinder. These two boilers have their peculiar disadvantages. A 

 cubic foot of water thoroughly charged with heat beeofnes 1,700 

 cubic feet of steam in an instant ; and so, whenever there is a rup- 

 ture, there is the greatest scattering of the adjacent parts. Tliere is 

 iinothcr objection to them, and that is, it is impossible to make them 



