PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 363 



nected to a steam wagon, the connection being made to a bar or transverse 

 spring- under the driving- axle, and the total weight of the drawn carriage 

 being about one-half on the driving wheels, but not resting on the springs 

 of the steam carriage, and thei'efore not afiecting the relative level of the 

 engines and driving axle. 



The act of parliament wisely prohibits projections on tires that work 

 on public roads; and it is not at all necessary to use them, except there 

 is greasy mud or ice or snow. On clean roads the adhesion is greater 

 than on railways, so much that the wheels of my steam carriage, which 

 would slip with 130 pounds on iron rails, do not slip with less than 180 

 pounds on pavements, and have gone up a hill over fresh broken stone with 

 190 pounds pressure, and without slipping. 



"Boydell's engine has what is called an endless railway, and its friends 

 claim that this secures it against slipping. I don't see how this can be; 

 the wheels run on iron rails, without other hold than common locomotives 

 have, unless the cycloids take the strain, and are made liable to be broken 

 by it. If this be the practice, I think the repairs will cost too much. 



For city traffic, except what ought to be carried at a speed equal to that 

 of passengers, so as not to hinder passenger carriages, I am confident 

 that gearing is not desirable. But if you wish to move boilers, columns, 

 buildings, and other bodies of over twenty tons, then it may be used; and 

 an advantage may be gained which has not yet been credited to steam — 

 you may move at a speed much slower than that at which horses work to 

 the best advantage; you may move at half a mile per hour, or less, and 

 thus avoid injury to pavements by jolting, and likewise avoid injury to 

 your wheels; and at the same time you may work with a small boiler. 

 Such slow vehicles should not be allowed in the principal thoroughfares 

 except at night. 



The cost of haulage by traction engines is given in Young's work enti- 

 tled " Steam on Common Roads." The reports in this book show that the 

 cost is from a tfiird to half the cost by horse power, at two and one-half 

 to three miles per hour, — that is, at the speed most advantageous for 

 horses. As the speed is made greater or less than this, the economy of 

 steam power, compared with horses, becomes greater. 



Second, as to noise. Horses' feet make more noise than the wheels of 

 light carriages, but less noise than the wheels of carts and omnibuses, and 

 about as much noise as the wheels of rail cars. The steam blast in 

 locomotives makes less than the noise of a tenth part of the horses that 

 would be required for equal work. But the steam blast may be silenced, 

 or dispensed with, and a fan substituted. The dummies of the Hudson 

 River railway condense their steam, and use fans. Grice & Long's" 

 steam cars use large cylinders, and make two turns to one turn of a thirty- 

 inch wheel, so as to expand the steam to a low pressure, and subdivide it 

 into very small puffs, and thus reduce the noise to an insensible amount. I 

 adopt the device of Gurney, which is, to exhaust into a chamber often or 

 twelve times the capacity of the cylinder, from which the exhaust flows 

 in a steady current like air from a smith's bellows, and makes no noise 

 except on steep inclines. It is generally believed that this arrangement 

 involves more back pressure than the usual puffing blast; but Mr. A. F. 



