power is enabled to propel the carriage. Like the resistance to the rolling motion, this adhesion is subject to much greater variation on common roads than on railroads; and to ascertain its practical power, that point must be taken at which its efficiency is at its lowest limit. This power of adhesion was Jong supposed to be so slight on common roads, that no considerable load could be impelled by its means. But more recent experience has proved that it is abundantly sufficient, under all ordinary circumstances, not only to propel the carriage, whose load rests upon the working wheels, but also to drag other carriages loaded in its train, ten times its weight on a railroad.
An obstacle was also anticipated to the practicability of this adaptation of the steam-engine, from the supposition that carriages thus constructed and propelled would occasion so rapid a wear and destruction of the turnpike roads, as to render the expenses of the repairs greater than any advantages to be derived from them could compensate. This objection, however, has also proved illusory. On the occasion of a steam-carriage being worked on the road between Gloucester and Cheltenham, for some months in the year 1831; those interested in turnpike roads procured the legislature to pass various acts of parliament, imposing prohibitory tolls on carriages propelled by machinery. A petition for the repeal of those acts was immediately elicited from Mr. Gurney, then the most enterprising and successful of the steam- carriage projectors. A committee of the House of Commons was appointed to receive evidence and to report on this petition; the result of which, was the report to which I have already alluded, and the consequent repeal of the prohibitory toll acts. By the evidence laid before this committee
