A centuky's progress of the steam engine. (>()8 



''safety boilers " are being improved and introduced at the close of 

 the century, we may confidently anticipate that standard pressures will 

 rise very rapidly until this revolution in boiler construction is com- 

 pletely effected. The twentieth century opens with the record for 

 costs of power reduced to 10 pounds of steam, nearly, per horse- 

 power per hour, and the next century will undoubtedly see the 

 approximation to the ideal case made much closer, while the ideal 

 costs will ])e as certainly reduced from 10,000 li. '!'. V. per hour, 

 nearly, to decidedly lower tigures. 



Gain must, however, be expected to be comparatively slow in the 

 coming- century, both because of the fact that the great wastes of the 

 beginning of the nineteenth century have already been largely I'educed, 

 leaving comparatively little opportunity to effect improvement in that 

 respect, and also because, under any circumstances, the progress of 

 improvement must always be at a constantly decreasing rate. If the 

 coming centur}^ sees the costs of the indicated horsepower reduced to 

 as little as 8,000 B. T. IT. per hour, or to 8 pounds of steam, or to 

 three-quarters of a pound of the best fuel, burned in the l)est boilers, 

 it will be probably quite as great an advance as can fairly be antici- 

 pated for the first century of the next millenium. 



