necessary to adapt a locomotive engine to propel carriages on turnpike roads may be easily inferred. Since the resistance of a given load to a propelling power is greater in a twelve-fold proportion than on a railroad, it follows, that with the same power the load drawn must be proportionally or twelve times less. But since a part of this load is the weight of the engine itself, and since this weight must bear some proportion to the entire load, it follows, that engines of equivalent power, to be adapted to common roads, must be lighter than those used on rail roads. But again, this consideration extends to the fuel and water as well as to the engine and boiler. Since a less quantity of water and fuel can be transported, a fresh supply must be taken in at shorter stages, of 6 or 8 miles. The railroad engines can travel about 20 miles without watering, and 30 without taking in fuel on a level railroad.
The steam coaches on common roads must be supplied with water and fuel every stage of 6 or 8 miles. The furnace being necessarily smaller and less powerful than those used in locomotive engines on railroads, the steam can be generated with sufficient abundance and rapidity, only by exposing to the action of the fire a much greater quantity of surface, in proportion to the whole quantity of water, than is attempted in engines on railways; and it is in the attainment of this object that the ingenuity of steam-carriage projectors has been for the most part displayed. It may, therefore, be interesting and useful at the present time, when we are on the eve of witnessing four attempts of steam-carriages on common roads, and when the practicability of the project has been recognised, and the conditions of its tolls regulated by the legislature, to describe one or
