the gas generator it reaches 12.7 per cent. From a theoretical point of
view the advantage therefore rests with the gas generator and gas motor.
In order to compare the net cost of the units of work, from an
industrial point of view, it is necessary to form estimates of
installation, costs of keeping in repair, interest and amortization.

Figs. 1 and 2 represent, on the same scale, the installations necessary
in each of these systems. The legends indicate the names of the
different apparatus in each installation. The following table shows
that, as regards the surface occupied, the advantage is again with the
gas generator and gas motor:

Steam Engine. Gas Motor.
Surface covered. 85 sq. m. 72 sq. m.
Surface exposed. 33 " 43 "
--- ---
Total surface. 118 " 115 "

The estimates of installation formed by Mr. Witz set forth the expense
relative to the capital engaged exactly at the same figure of 32,000
francs for a motive power of 75 effective horses. The expenses of
keeping in repair, interest, etc., summed up, show that the cost per day
of 10 hours is 47.9 francs for the steam engine and 39.6 for the gas
motor, say a saving of 8.3 francs per day, or about 2,500 francs for a
year of 300 days' work.

The gas motor, therefore, effects a great saving, while at the same time
occupying less space, consuming less water and operating just as well.

With Mr. Witz we cheerfully admit all the advantages that he so clearly