impossibilities, but always by their experiments and repeated failures
increasing knowledge, and forming a firm road upon which those following
them traveled to success.

In 1791 John Barber obtained a patent for an engine producing inflammable
gas, mixing it with air, igniting it, and allowing the current so produced
to impinge upon a reaction wheel, producing motion similar to the well
known Aelopile, which I have at work upon the table. About this time,
Murdoch (Jas. Watt's assistant at Birmingham) was busy introducing coal
gas into use for lighting; in 1792 Boulton and Watt's works were lighted
up with coal gas. From this time many gas engines were proposed, and the
more impracticable combustion of gunpowder received less attention.

In 1794 Thomas Mead obtained a patent for an engine using the internal
combustion of gas; the description is not a clear one, his ideas seem
confused.

In the same year Robert Street obtained a patent for an engine which is
not unlike some now in use. The bottom of a cylinder, containing a piston,
is heated by a fire, a few drops of spirits of turpentine are introduced
and evaporated by the heat, the piston is drawn up, and air entering mixes
with the inflammable vapor. A light is applied at a touch hole, and the
explosion drives up the piston, which, working on a lever, forces down the
piston of a pump for pumping water. Robt. Street adds to his description a
note: "The quantity of spirits of tar or turpentine to be made use of is
always proportional to the confined space, in general about 10 drops to a
cubic foot." This engine is quite a workable one, although the
arrangements described are very crude.

The first gas engine that was actually at work for some years; and was
applied to a variety of purposes, was Samuel Buren's. His patent was
granted in 1823, and in 1826 he built a locomotive carriage with which he
made several experimental runs in London; he also propelled a vessel with
it upon the Thames, and fitted up a large engine for pumping purposes. A
company was formed to introduce his engine, but it proved too wasteful of
fuel, and the company went into voluntary liquidation. Like almost all
engines of this time, the combustion of gas and air was used to produce a
vacuum, the piston being driven by atmospheric pressure.

Buren's locomotive carriage was thus in action three years before the
great trial in 1829, from which George Stephenson emerged victorious with
his wonde