From this time on, a continuous series of gas engine patents appear, 20 engines being patented between 1826 and 1860, which is the next date worthy of particular mention.
In this year, 1860, the famous "Lenoir" engine appeared. The use of high pressure steam engines had long been common, and Lenoir's engine was analogous to the high pressure engine, as Buren's was to the condensing engine. It created a very general interest, and many engines were constructed and used in France, England, and America; it resembled very much in external appearance an ordinary high pressure horizontal steam engine, and it was double acting.
During the following six years, other 20 British patents were granted, and the gas engine passed from the state of a troublesome toy to a practicable and widely useful machine.
From 1791 to the end of 1866, in all 46 British patents were granted for gas engines, and in these patents are to be found the principles upon which the gas engines of to-day are constructed, many years elapsing before experience enough was gained to turn the proposals of the older inventors to practical account.
The most important of these patents are:
| No. | Year. | ||
|---|---|---|---|
| Robert Street | 1,983 | 1794 | Direct-acting engine. |
| Samuel Buren | 4,874 | 1823 | Vacuum engine. |
| Samuel Buren | 5,350 | 1826 | Vacuum engine. |
| W.L. Wright | 6,525 | 1833 | Direct-acting engine. |
| Wm. Barnett | 7,615 | 1838 | Compression first proposed. |
| Barsante & Matteucci | 1,072 | 1854 | Rack & clutch engine. |
| Drake | 562 | 1855 | Direct-acting engine. |
| Lenoir | 335 | 1860 | D.I. engine, electric ignition. |
| C.W. Siemens | 2,074 | 1860 | Compression, constant pressure. |
| Hugon | 2,902 | 1860 | Platinum ignition. |
| Millein | 1,840 | 1861 | Compression, both constant vol. and pressure. |
| F.H. Wenham | 1,873 | 1864 | Free piston. |
| Hugon | 986 | 1865 | Flame ignition. |
| Otto and Langen | 434 | 1866 | Rack and clutch, flame ignition. |
Leaving for the present the history of the gas engine, which brings us to a stage comparable to the state of the steam engine during the Newcomen's time, it will be advisable to give some consideration to the principles concerned in the economical and efficient working of gas engines, in order to understand the more recent developments.
It has been seen that gunpowder was the explosive used to produce a vacuum in Huyghens' engine, and that it was abandoned in favor of gas by Buren in 1823. The reason of departure is very obvious: a gunpowder explosion and a gaseous explosion differ in very important practical points.
Gunpowder being a solid substance is capable of being packed into a very small space; the gas evolved by its decomposition is so great in volume that, even in the absence of any evolution of heat, a very high pressure would result. One cubic inch of gunpowder confined in a space of one cubic inch would cause a pressure by the gas it contains alone of 15,000 lb. per square inch; if the heating effect be allowed for, pressures of four times that amount, or 60,000 lb. per square inch, are easily accounted for. These pressures are far too high for use in any engine, and the bare possibility of getting such pressure by accident put gunpowder quite outside the purpose of the engineer, quite apart from any question of comparative cost. In a proper mixture of inflammable gas and air is found an exceedingly safe explosive, perfectly manageable and quite incapable of producing pressures in any sense dangerous to a properly constructed engine.
The pressure produced by the explosion of any mixture of gas and air is strictly determined and limited, whereas the pressure produced by the explosion of gunpowder depends greatly upon the relation between the volume of the gunpowder and the space in which it is confined.