shorter distance of the Admiralty and
Chelsea. Dead flats are found to be universally unfavourable; and
generally stations are useless nearly in the proportion of the miles
of dead flat looked over. On the contrary, stations between hill and
hill, looking across a valley, or series of valleys, are mostly clear;
and water surfaces are found to produce fewer obscure days than land
in any situation. The period least favourable of the same day is an
hour or two before and after the sun's passage of the meridian,
particularly on dead levels, where the play of the sun's rays on the
rising exhalations renders distant vision exceedingly obscure. The
tranquillity of the morning and evening are ascertained to be the most
favourable hours for observation.

A message from London to Portsmouth is usually transmitted in about
fifteen minutes; but, by an experiment tried for the purpose, a single
signal has been transmitted to Plymouth and back again in three
minutes, which by the Telegraph route is at at least five hundred
miles. In this instance, however, notice had been given to make ready,
and every captain was at his post to receive and return the signals.
The progress was at the rate of one hundred and seventy miles in a
minute, or three miles per second, or three seconds at each station; a
rapidity truly wonderful! The number of signals produced by the
English telegraph is sixty-three--by which they represent the ten
digits, the letters of the alphabet, many generic words, and all the
numbers which can be expressed by sixty-three variations of the
digits. The signals are sufficiently various to express any three or
four words in twice as many changes of the shutters.

The observers at these telegraphs are not expected to keep their eye
constantly at the glass, but look only every five minutes for the
signal to make ready. The telescopes are Dolland's Achromatics, at
which one would wonder, if every thing done for governments were not
converted into a job. The intention should have been to enable the
observer to see the greatest number of hours; consequently the light
should be intercepted by the smallest quantity of glass. Dollond's
achromatics contain, however, six lenses, and possess no
recommendation but their enlarged field, and their freedom from
prismatic colours in that field; points of no consequence in looking
through a fixed glass at a fixed and circumscribed object. The field
of the Galilean telescope is quite larg