boats; and guns are used as signals of approaching floods at freshet times
in various countries.

_Rockets._--As a signal in rock lighthouses, where it would be impossible
to mount large pieces of apparatus, the use of a gun-cotton rocket has
been suggested by Sir Richard Collinson, deputy-master of the Trinity
House. A charge of gun-cotton is inclosed in the head of a rocket, which
is projected to the height of perhaps 1,000 feet, when the cotton is
exploded, and the sound shed in all directions. Comparative experiments
with the howitzer and rocket showed that the howitzer was beaten by a
rocket containing twelve ounces, eight ounces, and even four ounces of
gun-cotton. Large charges do not show themselves so superior to small
charges as might be expected. Some of the rockets were heard at a distance
of twenty-five miles. Tyndall proposes to call it the Collinson rocket,
and suggests that it might be used in lighthouses and lightships as a
signal by naval vessels.

_Bells._--Bells are in use at every United States lightstation, and at
many they are run by machinery actuated by clock-work, made by Mr.
Stevens, of Boston, who, at the suggestion of the Lighthouse Board, has
introduced an escapement arrangement moved by a small weight, while a
larger weight operates the machinery which strikes the bell. These bells
weigh from 300 to 3,000 pounds. There are about 125 in use on the coasts
of the United States. Experiments made by the engineers of the French
Lighthouse Establishment, in 1861-62, showed that the range of bell-sounds
can be increased with the rapidity of the bell-strokes, and that the
relative distances for 15, 25, and 60 bell-strokes a minute were in the
ratio of 1, 1-14/100, and 1-29/100. The French also, with a hemispherical
iron reflector backed with Portland cement, increased the bell range in
the ratio of 147 to 100 over a horizontal arc of 60°, beyond which its