f water at different points in the rivers' courses,
and thus make it easy for river shipping to be moored safely in
anticipation of low water, when ignorance might lead to the grounding
of the boats on sand-bars or mud-banks. The notices of the probable
heights which freshets may reach, are followed by preparations upon the
"levees" and river-banks, to guard against overflows.

The United States Signal Service is a branch of the army. No one is
admitted to it who is under twenty-one years of age. Every candidate
has to undergo before enlistment an examination, the chief subjects of
which are spelling, legible hand-writing, proficiency in arithmetic,
and the geography of the United States, physical and political.

Successful candidates are regularly enlisted in the army, as
non-commissioned officers, and go through a course of very systematic
instruction in military signaling and telegraphy. They are assigned
afterward to different posts, where they are required to make
observations and report the same by wire three times a day, to the
commanding officer at Washington. These observations are made by means
of the instruments I have described, and include the different
appearances in the sky; and at all the stations they are made at the
same hour, according to Washington time. The telegraph gives to the
Herald of the Weather and his aids the advantage of hearing from all
the hundred and forty-odd observers almost at the same time; and when
all this information has been gathered up, studied out, and
re-arranged, the same swift servant takes all over the country, again
almost at one time, the ripe results of the care and watching of more
than seven score persons separated by hundreds and even thousands of
miles from the central office.

I should like to describe the instruments fully, but must content
myself with telling you what remarkable things some of them do. The
self-registering barometer, for instance, is made to actually
photograph a storm; another is made to draw with a pencil, every hour,
figures that show the height of the column of mercury and the
condition of the atmosphere. Even the vane, or weather-cock, marks down
the direction and force of the wind.

The report of the chief signal officer for the year 1876 gives
some idea of the vast amount of labor performed by the service.
The Herald of the Weather never rests. As he says, "The duties of this
office permit little rest and less hesitation. Its action mu