By this arrangement it might happen that the explosive mixture introduced into the cylinder might escape by the open exhaust valves. M. Bénier has obviated this difficulty by a novel device. Pure air is first admitted, driving out the products of combustion; the explosive mixture which follows is only admitted when the ports are closed. This result is obtained by properly regulating the supply of air and gas from the pump. One explosion therefore occurs in every revolution. The Bénier engine is constructed in sizes up to 100 horse-power, and also smaller ones of a few horse-power. A 5 horse-power motor consumes 800 grammes of anthracite per horse-power hour: this result is very remarkable, because great difficulty has been found in working these small engines at all with poor gas; the gas generator seems to work badly when its dimensions are so small. A 15 horse-power motor only consumes 600 grammes per horse-power hour. The Bénier combined plant shown in Figs. 49 and 50 has received a most flattering reception on the Continent, and there is good reason to believe that it will be very much more widely used in the future. We close this chapter with a table setting forth the relative merits and economy of a number of motors. ----------------+----------+-------+-------------+------------+------+---------- | | | | | Cost | | Nature | Power | |Consumption | per | Trials Type of Engine. | of |of the | Consumption | per |horse-|conducted | Fuel. |Engine.| of Fuel. |horse-power |power | by | | | | hour. |hour, | | | | | |pence.| ----------------+----------+-------+-------------+------------+------+---------- Lenoir (1860) | Coal gas | ·9 | 2400 litres| 2700 litres| 9 |Tresca Hugon (1866) | ” | 2·07 | 5400 ” | 2600 ” | 8·5 | ” Langen and Otto | ” | ·46 | 660 ” | 1380 ” | 4·5 | ” (1867) | | | | | | Wittig and Hees | ” | 4 | 4960 ” | 1240 ” | 3·5 |Brauer (1881) | | | | | | Koerting- | ” | 2·18 | 2700 ” | 1275 ” | 3·7 |Schettler Lieckfeld | | | | | | Otto | ” | 8·34 | 9500 ” | 915 ” | 2·8 |Allard and | | | | | | Potier Dugald-Clerk | ” | 11·6 | 9700 ” | 877 ” | 2·5 |Sterne (1884) | | | | | | Lenoir (1885) | ” | 2 | 1320 ” | 655 ” | 1·9 |Tresca Simplex (1885) | ” | 9·41 | 5580 ” | 593 ” | 1·1 |Witz ” ” | Dowson | 3·66 | 6040 ” | 3300 ” | ·7 | ”