996 Trans A ctions of the A mericax Institute. 



from the heating surfaces would be 1X912, or 912 i^ouuds of water 

 per minute. The steam generator invented by the speaker, is com- 

 posed of inclined tubes suitably arranged over the furnace. The 

 water circulates up througli the lower tubes, parts with its steam at 

 the upper ends of the tubes, and returns to the lower ends of the 

 lower tubes again by the tubes which have their upper ends at or 

 near the water line. The connections between the tubes at their 

 ends form chambers with contractive openings or communications, 

 which serve to prevent the violence of the circulation from projecting 

 the water into the steam room and causing the boiler to prime or 

 work water. The amount of circulation varies with the inclination 

 at which the tubes are set. The amount of water that the opening 

 at the end of any tube will pass M'hen set at the proper inclination is 

 fully twenty-six cubic feet per minute, wliich is sufficient for all 

 practical purposes; but the amount of circulation can be increased to 

 three times that amount by adding extra connections at the ends of 

 the tubes, which does not reqnire any change as to the principle or 

 form of the connection. A boiler should be so constructed that a 

 steam bubble should not be formed lower than two feet from the top 

 of the water. He had never seen it stated what the amount of water 

 circulation should be for every pound of pressure. The small amount 

 of water that is over the crown sheet of the Martin boiler would seem 

 to be too much heat for too little water. Boilers scale where the 

 heat is greatest, and the circulation rapid. When water rises to a 

 certain temperature, it crystallizes and leaves a scale. 



Mr. John A. Coleman said he had listened to the discussion on the 

 circulation of water in steam-boilers, and the whole subject seems to 

 be involved in a mystery. Let us now view the matter in another 

 light. The first problem in steam engineering is to produce heat, 

 tlie next to make the water absorb it. A square foot of iron will 

 transmit a given quantity of caloric, two square feet twice as much, 

 and so on. When we shovel coal on a grate it is to get heat, and 

 that object is rarely well done. We put coal on a grate and combus- 

 tion ensues, and the gases pass off very rapidly. If 'the draft is very 

 strong much combustible matter is carried up the chimney before it . 

 can be mixed with the i*equisite amount of oxygen, without which 

 there cannot be perfect com1)U3tion. Tlie bottom of a pot over the 

 fire may be considered the best form of heating surface ; the old 

 cylinder-boiler is the same in principle, and in sufficient numbers 

 will make steam as well as any other kind of boiler in existence. 



