Page:Popular Science Monthly Volume 18.djvu/231

Rh character, and this necessitates a machine that will always be ready for work, or that can be made ready with but little trouble at short notice, and that is no expense, or but very small expense, when not being used. It needs further to be perfectly safe, economical in use, of low first cost, and to require but little care, and that of a kind which can be given by unskilled labor.

The attempts to make a machine that would answer to these varied requirements have been many, and they have been crowned with greater or less success. Though it can not be said that the ideal motor has been produced, still there are at present made and on the market a number of machines of real merit, and some of great excellence, that are all well adapted to the needs of users of light power, including the householder. While in large manufacturing only two machines—the water-wheel and the steam-engine—can be used, for the purpose of these small powers the range is much greater. Wind and water, steam, hot air, gas, and electricity, are all suitable and are all to a greater or less degree available. I propose in these papers simply to make a brief description of some of the more promising and successful machines now on the market, and give such information regarding the sizes in which they are made, cost of working, and prices, as will be of value to the householder and others having use for such a power.

Though the windmill is one of the oldest of the appliances by which man has sought to turn to his use the powers of nature, it remained until a comparatively recent period a very crude and cumbersome machine. In the earliest form, the wheel was fixed so that it could only turn when the wind was in the right direction; and later, when it was made movable, the shifting had still to be done by hand as often as the wind veered. Successive improvements were, however, slowly made, the chief ones being the addition of a rudder-vane placed directly behind the wheel in a vertical plane at right angles with its face, and a centrifugal governing device by which the canvas sails were furled and unfurled as the wind varied in strength. The pressure of the wind upon this vane automatically shifted the wheel into the wind, and the action of the governor presented to it a greater or less surface of the sails, securing a uniform velocity with varying wind-pressure. Even with these great improvements the windmill remained a clumsy affair until it was developed by American skill and ingenuity into the present very serviceable machine. As now made it is light and strong, and entirely automatic in answering to the varying direction and pressure of the wind. The canvas sails have given place to light wooden slats arranged radially around the wheel at short distances apart, and the whole mechanism has been simplified and vastly improved both in construction and design. The tower is an open-work structure of wood or iron, easily erected and taken down when desired.

Two methods of regulating the extent of wheel-surface exposed to the wind are now in use, the one acting by centrifugal force as in