Water Power.— It is estimated that there are available in this country about 61,000,000 water horse power that could be profitably util ized, of which it appears that only 6,5t10,000 horse power have been developed; that is, practically 54,000,000 water horse power is now going to waste. Nor does it seem likely that this power will soon be developed unless more satisfactory legislation be enacted which will afford a greater security and permit a better return to the investor in water-power develop ment.
Electric Power.—The statistics of American manufacturing, compiled for the 1900 United States census, show that at that time electric power was less than 5 per cent of all that was in use in such plants, or about 500,000 horse power out of a total of 11,000,000. During the decade from 1899 to 1909 the total amount of primary power used in the industries out the United States has increased from 11,000,000 horse power to nearly 19,000,000, of which 76 per cent or a little over 14,000,000 horse power is derived from steam engines; the rest being distributed between water power, electric power and gas and internal combustion engine power. At the time of the last census there were in use in the industries nearly 5,000,000 horse power in electric motors, of which over 3,000,000 horse power, or 63 per cent, was generated by the particular establishment using the power. That is, 63 per cent of the electric power used in the industries is generated by the user, and 37 per cent is purchased. The introduction of electric power in machine shops and factories was at first looked upon with disfavor and was opposed by many manufac turers, but the innovation obtained a foothold, and advantages which were at first unforeseen were found to attend its use, so that now it is being very generally adopted for a wide variety of work. A considerable difference of opinion exists as to whether individual motors should be used with each machine, or whether a num ber of machines should be arranged in a group and driven from a short line shaft. There are well-defined conditions to which each system is best adapted, but there are wide limits be tween which there appears to be no general rule, and both methods are occupying the same field. For isolated machines and for heavy machines that may be in occasional use, the in dividual motor is narticularly well adapted, as it consumes power only when in operation. It is, however, necessary that each motor thus Connected shall be capable of supplying suffi cient power to operate its machine under the heaviest as well as lightest loads. In certain
cases, moreover, the load is liable to very great irregularity, as for instance in metal-working planers, in which the resistance offered by the machine at the moment of reversal of the platen is far higher than at other times, and may be so great as to endanger the armature of the motor. Under these conditions it is necessary to use a motor of much larger ca pacity than the average load would indicate. Ordinarily in machine driving the motor is shunt-wound, and the current through the field coils is constant under all conditions of load; but to obtain the best results with that Class of machinery in which tfie load is intermittent and subject to sudden variations, the motor should be compound-wound so as to increase the torque without an excessive increase of current in the armature. In many cases with individ ual motors, owing to wide variations in power required, the average efficiency of the motor may be very low; for this reason a careful cone sideration of the conditions governing each case indicates that for ordinary machine-driv ing, especially with small machines, short lengths of light shafting may be frequently em ployed to good advantage, and the various ma chines, arranged in groups, may be driven from one motcir. By this method fewer motors are required, and each may be so proportioned to the average load that it may run most of the time at its maximum efficiency. When short lengths of shafting are employed the alignment of any section is very little affected by local settling of beams or columns, and since a rela tively small amount of power is transmitted by each section, the shaft may be reduced in size, thus decreasing the friction loss. Moreover, with this arrangement, as also with the inde pendent motor, the machinery may often be placed to better advantage in order to suit a given process of manufacture; shafts may be placed at any angle without the usual compli cated and often unsatisfactory devices, and set ting-up room may be provided in any suitable location as required, without carrying long lines of shafting through space. This is an important consideration, for not only is the running ex pense reduced and the lighting increased thereby, but the clear head-room thus obtained, free from shafting, belts, ropes, pulleys and other power-transmitting devices can be more easily utilized for hoists and cranes, which have so largely come to be recognized as essential to economical manufacture.