base, it might easily become a serviceable motor for domestic use. As the quantity of oil used in such a machine would be small, it need not be in any way more dangerous than an ordinary lamp or oil-stove, and if properly finished would probably require but little more care. The oil used would of course have to be of a high grade, such as is used or should be used in lamps, and would cost considerably more than that suitable to the larger machines, but the expense of running would still be quite small.
Such are some of the best of the machines which the demand for comparatively small motors has, up to the present, called forth, and in the list those desiring such a power can scarcely fail to find something tolerably well suited to their wants. The various forms of heat-engines have been brought very close to the limit of possible simplicity, and show with some clearness what may be expected from further development along the same lines. They have been mainly designed to meet the requirements of industrial users, because the largest and most constant demand is from these; but they are all capable of a reduction to the scale suitable in the household. For this purpose the gas-engine appears, on all accounts, to be the best adapted. Efficient and serviceable heat-engines are, of necessity, somewhat complicated, and require in their main parts an excellence and accuracy of workmanship that make it difficult to construct them cheaply. The gas-engine seems to be susceptible of greater simplicity of construction than any other of these, and can therefore be made at less cost. Present prices are undoubtedly high, but, with a sufficient demand and the competition that would result, they would decrease considerably, and it is not improbable that an efficient and economical machine of about one man-power could, under such conditions, be furnished at a price not exceeding fifty dollars.
But it is doubtful if such a machine would, after all, be the most satisfactory solution of the problem of a domestic motor. The final solution, there is reason to believe, is to be found, not in a heat-engine of any kind, but in a machine that will simply apply, in a convenient form and economical way, a power already furnished. Of such a nature is the water-wheel, which, for simplicity of construction, ease of handling, high efficiency, and small first cost, is unapproached by anything at present, and will probably never be surpassed by any future device. If water under sufficient pressure were everywhere obtainable, there would be no need of looking beyond this very simple and perfect contrivance. Water-power is, however, limited, and is generally least available where small motors are most wanted—in populous cities. Doubtless in many locations, where the windmill is employed to supply water to a house, a combination of wind and water power might readily be made which would prove quite satisfactory. A windmill of considerable power could be used to pump water into a properly elevated reservoir, or into a force-tank, from which it could be distributed to