In a brief account, given by himself, of his experiments in steam, he says: "I could break and grind three hundred bushels of plaster of paris, or twelve tons, in twenty-four hours; and to show its operations more fully to the public, I applied it to saw stone, on the side of Market Street, where the driving of twelve saws in heavy frames, sawing at the rate of one hundred feet of marble in twelve hours, made a great show and excited much attention. I thought this was sufficient to convince the thousands of spectators of the utility of my discovery, but I frequently heard them inquire if the power could be applied to saw timber as well as stone, to grind grain, propel boats, etc., and though I answered in the affirmative, they still doubted. I therefore determined to apply my engine to all new uses; to introduce it and them to the public. This experiment completely tested the correctness of my principles. The power of my engine rises in a geometrical proportion, while the consumption of the fuel has only an arithmetical ratio; in such proportion that every time I added one-fourth more to the consumption of the fuel, its powers were doubled; and that twice the quantity of fuel required to drive one saw, would drive sixteen saws at least; for when I drove two saws the consumption was eight bushels of coal in twelve hours, but when twelve saws were driven, the consumption was not more than ten bushels, so that the more we resist the steam, the greater is the effect of the engine. On these principles very light but powerful engines can be made suitable for propelling boats and land carriages without the great encumbrance of their weight as mentioned in Latrobe's demonstration." In the year 1840, Evans, by order of the Board of Health of Philadelphia, constructed at his works, situated a mile and a half from the water, a machine for cleaning docks. It consisted of a large flat or scow, with a steam engine of five horse-power on board, to work the machinery to raise the mud into the scows. This was considered a fine opportunity to show the public that his engine could propel both land and water conveyances. When the machine was finished, he fixed, in a rough and temporary manner, wheels with wooden axletrees, and, of course, under the influence of great friction. Although the whole weight was equal to two hundred barrels of flour, yet his small engine propelled it up Market Street and round the circle to the waterworks, where it was launched into the Schuylkill River. A paddle-wheel was then applied to its stern, and it thus moved down that river to the Delaware, a distance of sixteen miles, leaving behind all vessels that were under sail.