We asked the Library of Congress for a picture of the Otto
engine, which is considered the first practical power unit among
internal combustion engines. The picture shown here was sent. It is
identified as illustrated in Scientific American, possibly in the
1870s.
Below is the article that appeared with the picture.
The successful gasoline engine should, first of all, be so
constructed as to prevent any leak of gasoline either in vapor or
fluid form, and it should besides be simple in design and reliable
in operation for each function belonging to the cycle of work of
the engine. The Otto Gas Engine Works, of Philadelphia, who have
made a national reputation on their Otto gas engines, have
endeavored to meet these conditions, and the engine herewith
illustrated represents the smallest size of such an engine which
they have recently placed on the market. No separate apparatus is
used for producing vapors, but the gasoline is conveyed to the
engine from a supply tank placed outside of building, and only
mixes with air when it reaches the engine cylinder, where it is
fired at once.
The igniting is done by a hot tube, which has been found so
efficient a device with the modern Otto gas engines, and this tube
is heated by a flame, similar to that produced in gasoline stoves,
and surrounded with the same precautions for safety. The Otto
gasoline engine is also fitted for electric ignition, and the
engine is so arranged that it can be furnished with either form of
igniter as desired.
Among the sizes offered by the Otto Gas Engine Works some are
specially designed for electric lighting, running at high speed and
adapted for use in country residences, hotels, public gardens and
grounds, etc. Other sizes have been made of portable design and are
available as farm or contractors’ engines, for thrashing, hay
baling, pumping for irrigation, etc. The size illustrated is of
about four horse power, and this size has been in demand from grain
dealers for running elevators, conveyors, feed mills, corn
shellers, etc. The running expense is of course very low, and as
compared with gas engines the cost corresponds to that of gas at 60
to 80 cents per 1,000 c. ft., gasoline being 8 to 10 cents per
gallon.