It is now more than half a century ago that Otto first built internal combustion engines using the four-stroke cycle, and the economy of these engines was early recognized as being far superior to that of the steam engine in thermal units required. Before the days of the universal use of gasoline, gas was the only fuel used in such engines, and the difficulty of making suitable producer gas for them stood in the way of their earlier introduction.

In the case, however, of blowing engines for blast furnaces, which are in one sense only gigantic gas producers, the advantages of using the gas they supply directly in the engine cylinders are obvious. The first suggestion to carry out this plan was made in 1876 by Mr. Frank Firmstone, then manager of the Glendon Iron Works, to Mr. P. L. Weimer, of Lebanon, an engine builder of some note, but nothing was done in the way of carrying it out for nearly twenty years, when in 1895 Mr. B. H. Thwaites in England installed a small gas engine and operated it continuously for a considerable period on blast-furnace gas.

The idea was then taken up by German and Belgian engineers and to them is due the credit for overcoming the enormous technical, mechanical and financial difficulties involved in carrying this simple scheme into successful practice.

It was only after engines of this type had reached a high state of development in Europe that they were introduced into this country, a circumstance which has caused much shame to some good Americans, but I believe does not reflect as much discredit upon this country as has frequently been claimed, on account of differences in conditions unnoticed by casual observers.

These differences are financial and industrial rather than technical, and consist in the fact that in Europe capital can earn only a relatively small rate of interest and labor only a small rate of wages compared with what both command in this country, while raw materials, particularly coal, are scarce and dear in Europe and have in the past been ridiculously cheap in this country.

The saving to be made must be bought, as we shall presently see, at the price of enormous expenditures in capital and in high-priced skilled labor, while its value could only be measured in terms of the saving in coal, one of our cheapest commodities.

When these technical savings were reduced by the amount of the high labor cost required to make them, the interest which the balance would pay on the capital involved was often less than could be earned by that capital in increasing the producing capacity of the plant.

It is true that this view of the subject involves the use of coal which might be saved for future generations by the other system but this is a subject to follow which would take us far beyond the proper boundaries of this work and I shall not attempt to analyze it further than to suggest that, admitting the value of the "conservation" idea, it is proper to ask whether the saving of money, which represents value already created, may not be as justifiable as the saving of raw material which only has potential value.

Or to put the matter in different form, if the owner of a plant can make more interest on the capital invested by using more raw material than is theoretically necessary, who is to compensate him for the loss he makes by following the opposite course?

On the other hand, this policy is capable of great abuse, and Americans, as a nation, have had in the past and to some extent have even yet a tendency to prodigality and to ignore savings of various kinds which they might make, more through mental inertia than through any more worthy motive.

It may be admitted that the policy of conserving capital at the expense of raw material has often been carried too far, and the gas engine may be such a case. I shall give at the end of this chapter an outline of the method by which this question may be settled on its merits in each individual case.