notwithstanding all this the wheels never came off the line. The
sections of line were taken up and replaced as the boat advanced, and a
speed of 1,100 yards per hour was attained. Dr. Balay and M. Mizon
declared that the result obtained exceeded by far their most sanguine
hopes, because during their last voyage, the passage of the rapids had
sometimes required a whole week for 1,100 yards (1 kilometer), and they
considered themselves very lucky indeed if they could attain a speed of
one kilometer per day. The same narrow gauge system has since been three
times adopted by African explorers, on which occasions it was found that
the 20 in. line, with 9 lb. or 14 lb. rails, was the most suitable for
scientific expeditions of this nature.

The trucks used are of the kind usually employed for military purposes,
with wheels, axles, and pivot bearings of steel; on being dismounted the
bodies of the two trucks form a chest, which is bolted together and
contains the wheels, axles, and other accessories. The total weight of
the 135 yards of road used by Dr. Balay and M. Mizon during their first
voyage was 2,900 lb., and the wagons weighed 5,000 lb. Hence the
expedition had to carry a supplementary weight of 3½ tons; but at any
given moment the material forming this burden became the means of
transporting, in its turn, seven boats, representing a total weight of
20 tons.

It is impossible to enumerate in this paper all the various kinds of
wagons and trucks suitable for the service of iron works, shipyards,
mines, quarries, forests, and many other kinds of works; and we
therefore limit ourselves to mentioning only a few instances which
suffice to show that the narrow gauge can be applied to works of the
most varied nature and under the most adverse circumstances possible.