THE CONQUEST OF NATURE 



Eleventh and Twelfth censuses, amounting to 1,510.9 

 per cent. 



"Within the past decade, and more particularly 

 during the past five years, there has been a marked in- 

 crease in the use of this power in industrial establish- 

 ments 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, doubt- 

 less, 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 statis- 

 tics 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 num- 

 ber of small engines for various purposes. 



"The large increase in the use of internal-combus- 

 tion 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 



