great symmetrical barometric wave of November. At its setting in the
barometer is generally low, sometimes below twenty-nine inches. This
depression is generally succeeded by _two_ well-marked undulations,
varying from one to two days in duration. The central undulation, which
also forms the apex of the great wave, is of larger extent, occupying
from three to five days; when this has passed, two smaller undulations
corresponding to those at the commencement of the wave make their
appearance, and at the close of the last the wave terminates." With but
slight exceptions, the observations of eight successive years have
confirmed the general correctness of this type. On two occasions the
central apex has not been the highest, and these deviations, with some
of a minor character, form the exceptions alluded to. This type only has
reference to London and the south-eastern parts of England; proceeding
westward, north-westward, and northward, the symmetrical character of
this type is considerably departed from; each locality possessing its
own type of the barometric movements during November. The desiderata in
immediate connexion with the November movements, as observed in the
southern and south-eastern parts of England, that present themselves,
are--the determination of the types for November, especially its middle
portion, as exhibited on the oceanic surface within an area comprised
between the 30th and 60th parallels, and the 1st and 40th meridians
west. Vessels sailing within this area may contribute greatly to the
determination of these types by making observations at intervals of
three hours from the 1st of November to the 7th or 8th of December. The
entire period of the great symmetrical wave of November will most
probably be embraced by such a series of observations, as well as the
annual depression of the 28th. For the elevation of the 25th of December
the three-hourly observations should be commenced on the 21st, and
continued until the 3rd or 4th of the succeeding January.