364 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Smith, who tried it on the Lehigh Valley railway, considers that its loss 

 by back pressure is not sensibly greater than the loss by the usual blast- 

 pipe. 



There is a relation between gearing and the steam blast. Mr. Wm. S. 

 Hudson, superintendent of the Sogers' Locomotive Works, approves of 

 gearing for the traction engines, to such extent as to make a quick succes- 

 sion of small pufts, rather that a slow succession of large puffs, because 

 the quick puffs keep a constant and nearly equable current of air through 

 the fire, and the strong puflt's, at long intervals, alternately disturb the fire, 

 and throw out coals, and then leave the draft weak until the next strong 

 discharge of steam. 



Now, by the plan of Gurney, the exhaust chamber may be made to 

 equalize the draft, if it be proportioned to the time between the puffs. 

 If the engine has large 'wheels, and move slowly, the exhaust chamber 

 must be large; if it move at moderate speed, a small chamber will suffice; 

 if it make four or five turns per second, no chamber is needed. There- 

 fore, the complexity of gearing is not necessary to equalize the draft; it 

 is not so effective an equalizer as the exhaust chamber or the fan, nor is it 

 so silent.- 



Lifting sparks is an evil to be carefully avoided in street engines. It is 

 a nuisance that ought to prohibit any engine which is not nearly free from 

 it. It is to be avoided, partly, by avoiding such fuel as wood, charcoal 

 and gas coke, and by using solid anthracite, and hard coke that is made 

 expressly for locomotives. When I burn charcoal in my steam carriage 

 at night, it throws out sparks to such an extent as to light the road 

 sufficiently; and when a steam fire engine which burns wood, has worked 

 an hour, you may see the pavement strewn with charcoal all around it. 



It is also partly avoided by a large grate and a deep fire box. The 

 dummies on the Hudson River railway have fire boxes forty inches deep, 

 I design them from thirty to thirty-six inches deep for the small boilers of 

 steam carriages; and my observations have been sufficient to satisfy me 

 that large grates, deep fire boxes, heavy and tough fuel, and a steady 

 draft, will make a cleanly engine; and that the dirt from thirty steam cars 

 will be less than the dust worn from the pavement by one horse. 



Third: as to smoke, or carbonic acid and nitrogen. The seven horses ol 

 an omnibus, in the twenty-four hours, mix into the street air more carbonic 

 acid than a steam omnibus would mix into it, and the nitrogen is in pro- 

 portion, because the car would project its gases upward with such 

 Telocity that they would soon be carried over the city, whereas the horses 

 blow their breath downward, and mix it with the air we have to breathe. 

 The gas nuisance is, therefore, much the greatest with horse power. As 

 to smoke, it is a disgrace to the railroad companies that they have allowed 

 it in cities. They had only to use coke, while in the streets, in order to 

 avoid smoke; and, had they done so, there would have been no objection 

 to their using locomotives in the streets of New York, as they were allowed 

 to do in Brooklyn until their indecency disgusted the people, and the 

 people drove them off. On rails, and still more on iron floors, the friction 

 covdd be lessened, so that the power, and therefore the gases, would be 

 reduced to a third of what they must be on stone pavements. 



