"Within the past decade, and more particularly during the past five years, there has been a marked increase in the use of this power in industrial establishments for driving machinery, for generating electricity, and for other kindred uses. At the same time, internal-combustion engines have increased in popularity for uses apart from manufacturing, and the amount of this kind of power in use for all purposes in 1900 was, doubtless, very much larger than indicated by the figures relating to manufacturing plants alone. "The average horse-power per gas engine in 1900 was 9.7 horse-power. There are no available statistics upon which to base a comparison of this average with the average for 1890, but it is doubtful if there has been any very material change in ten years; for while gas engines are built in much larger sizes than ever before, there has been also a great increase in the number of small engines for various purposes. "The large increase in the use of internal-combustion engines has been due to the rapid improvements that have been made in them, their increased efficiency and economy, their decreased cost, and the wider range of adaptability that has been made practicable. "Steam still continues to be preeminently the power of greatest importance, and the census returns indicate that the proportion of steam to the total of all powers has increased very largely in the past thirty years. In 1870 steam furnished 1,215,711 horse-power, or 51.8 per cent of a total of 2,346,142; in 1880 the amount of steam power used was 2,185,458 horse-power out of a total of 3,410,837, or 64.1 per cent; in 1890 out of an aggregate of 5,954,655 horse-power, 4,581,595, or 76.9 per cent was steam; while in 1900 steam figured to the extent of 8,742,416 horse-power, or 77.4 per cent, in a total of 11,300,081. This increase in thirty years, from 51.8 per cent to 77.4 per cent of the total power, shows how much more rapidly the use of steam power has increased than other primary sources of power. "The tendency toward larger units in the use of steam power is shown inadequately by the increase in the average horse-power per engine from 39 horse-power in 1880, to 51 horse-power in 1890, and 56 horse-power in 1900.