d 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 deg., beyond which its
effect gradually diminished. The actual effective range of the bell sound,
whatever the bell size, is comparatively short, and, like the gong, it is
used only where it needs to be heard for short distances. Mr. Cunningham,
Secretary of the Scottish Lighthouse Establishment, in a paper on fog
signals, read in February, 1863, says the bell at Howth, weighing 21/4 tons,
struck four times a minute by a 60 pound hammer falling ten inches, has
been heard only one mile to windward against a light breeze during fog;
and that a similar bell at Kingston, struck eight times a minute, had been
so heard three miles away as to enable the steamer to make her harbor from
that distance. Mr. Beaseley, C.E., in a lecture on coast-fog signals, May
24, 1872, speaks of these bells as unusually large, saying that they and
the one at Ballycottin are the largest on their coasts, the only others
which compare with them being th