[A Report under the foregoing title was made by the Commissioner of Corporations (U. S. Bureau of Corporations) and published March 14, 1912. Some extracts are here taken from the summary on pages 1-34.]

Physical facts involved. Prior to the discovery of electrical transmission of power over long distances, water-power could be utilized only at the power site. This limited its development in most cases to comparatively small units, and almost exclusively to manufacturing enterprises. The introduction of electric-power transmission not only provided a means of supplying distant manufacturing and domestic demands, but also opened up an entirely new power field, namely, the operation of street railways and lighting plants, and enormously increased the relative importance of water-power. Thus the development of water-power (based on installed wheel capacity) for railway and lighting purposes increased from 487,000 horse-power in 1902 to 1,441,000 horse-power in 1907 (the latest date for which statistics are available), or by nearly 200 per cent. In manufacturing industries, where transmission by electricity is infrequent, water-power development during the period 1900-1905 increased by only 11 per cent.

These comparisons suggest the remarkable influence that electrical transmission has had upon the development of water-power in recent years, and at the same time they indicate the peculiarly close natural relationship between the water-power industry and public-service enterprises.

This growing importance of the "commercial" use of water-power, its comparatively recent development and the consequent lack of an appreciation of its real significance, together with the established connection between commercial water-power enterprises and public utilities, all demand that the public be furnished with accurate and comprehensive information on this subject. This report is an attempt to meet that demand. . . .

Estimates of potential power. The United States Geological Survey estimated the "minimum potential" water-power of the country at 36,916,250 horse-power, and the "assumed maximum" at 66,518,500 horse-power, both figures excluding storage possibilities. "Storage," as used in this report, means the extensive storage of water in large reservoirs so as to regulate the stream flow over considerable periods. It does not refer to the small accumulation of water in a power dam; this is referred to as "pondage." These Survey estimates of potential power were arrived at by multiplying the flow of the stream into 90 per cent of the fall. . . .

Revision of Survey figures. The Survey estimates require some revision. . . . Reducing the estimates of the Survey accordingly, the totals become 26,736,000 horse-power and 51,-398,000 horse-power, minimum and maximum, respectively. . . . As noted above, no allowance for storage has been made in these Survey estimates. Various estimates including storage have been made, but most of them are exceedingly extravagant, and none of them is based upon sufficiently reliable data to warrant unquestioned acceptance. . . .

The water-power centers of the country are the Pacific Coast and intermountain States, the New England States and New York, the Great Lakes Region, and the States entered by the Southern Appalachian Range. Approximately 43 per cent of the total estimated minimum power of the country is found in California, Oregon, and Washington. Adding to this the power in Montana, Wyoming, and Idaho gives 60 per cent, of the total minimum power in these six States.

Power demand. The total installed stationary prime-moving power of all kinds (steam, gas, and water) in the

United States in 1905-1907 (the latest date for which complete statistics are available) was approximately 23,000,000 horse-power. Of this, 18,858,000 horse-power or 82 per cent of the total, was generated from steam; 3,423,000 horsepower, or 15 per cent was developed from water; while 631,000 horse-power or about 3 per cent was generated from internal-combustion engines. It will be seen, therefore, that only about one-seventh of the total power demand of the country was at that time supplied by water. It seems highly probable that the rapid development of water-power since 1907 has increased its proportion of the total installed prime-moving power. . . .

Developed water-power in the U. S. [page 5]. There is a marked geographical concentration of developed water-power (as well as the similar concentration of potential power set forth above). Thus, nearly 50 per cent of the developed "commercial" water-power of the country is located in five States, as follows:

An even more marked concentration of developed water-power employed in manufacturing is shown by the following summary :

Some problems of water-power development. Certain physical and economic facts must be recognized in discussing

water-power possibilities. The production and consumption of power are simultaneous. It is not possible practically to store overproduction for future demands when production may be light. The three principal demands for power are lighting, traction, and manufacturing. If the greatest demand from each of these three sources came at a different period of the day, the total would be so distributed as greatly to reduce the required maximum capacity of the power plant. As a matter of fact, neither of these demands is uniform, while they more or less overlap. Thus, the demand for power for lighting tends to reach a maximum about the time that the demand for transportation is at its height. This overlapping creates what is known as the "peak of the load." It is imperative, therefore, to provide sufficient power to meet this maximum demand. Aside from these daily fluctuations in the power market, there is also a seasonal fluctuation. The demand in winter is greater than in summer. The daily fluctuation, moreover, is greater in winter.

In addition to this fluctuation in the demand there is also a variation in the supply of water-power available. This is due to the fluctuating flow of streams. The flow varies according to the location and character of the drainage basin and according to seasons, and the seasons themselves, of course, vary in different years. A water-power installation, therefore, must also take these factors into account. If the installation provides only for utilizing the minimum flow there must be a tremendous waste of energy during the period of larger flow. On the other hand, as already stated, it is impracticable to install power up to the maximum potentially available.

Remedy for variations in supply and demand for power. The problem of a power producer is to meet these varying conditions of demand and supply in the most economical way. There are several means contributing to this end.

The physical effect of irregularity in the flow of the streams can be partly overcome by storage. In no case, however, can storage give a stream anything like the power represented by its maximum flow. The amount of storage practicable depends upon the topography of the country and upon the value of the lands overflowed. Up to this time very little progress has been made in storage development.