A Treatise on Meteorological Instruments: Explanatory of Their Scientific Principles, Method of Construction, and Practical Utility — John Shaqi
A Treatise on Meteorological Instruments: Explanatory of Their Scientific Principles, Method of Construction, and Practical UtilityNegretti, Enrico Angelo Lodovico
Science
A Treatise on Meteorological Instruments: Explanatory of Their Scientific Principles, Method of Construction, and Practical Utility
Negretti, Enrico Angelo Lodovico
Meteorological instruments; Meteorology; Scientific apparatus and instruments
Barometers may now be seen attached to drinking fountains, properly
protected, and are frequently consulted by the passers-by. But it is among
those whose lives are endangered by sudden changes in the weather,
fishermen especially, that the warning monitor is most urgently required.
Many poor fishing villages and towns have therefore been provided by the
Board of Trade, at the public expense, and through the humane effort of
Admiral FitzRoy, with first-class barometers, each fixed in a conspicuous
position, so as to be easily accessible to all who desire to consult it.
Following this example, the Royal National Life Boat Institution has
supplied each of its stations with a similar storm warner; the Duke of
Northumberland and the British Meteorological Society have erected several
on the coast of Northumberland; and many other individuals have presented
barometers to maritime places with which they are connected.
These barometers have all been manufactured by Messrs. Negretti and
Zambra. The form given to the instrument seems well adapted for public
purposes.
[Illustration: Fig. 12.]
=15. Fishery or Sea-coast Barometers.=--Fig. 12 gives a representation of
these coast and fishery barometers. The frame is of solid oak, firmly
screwed together. The scales are very legibly engraved on porcelain by
Negretti and Zambra's patent process. The thermometer is large, and easily
read; and as this instrument is exposed, it will indicate the actual
temperature sufficiently for practical purposes. The barometer tube is
three-tenths of an inch in diameter of bore, exhibiting a good column of
mercury; and the cistern is of such capacity, in relation to the tube,
that the change of height in the surface of the mercury in the cistern
corresponding to a change of height of three inches of mercury in the
tube, is less than one-hundredth of an inch, and therefore, as the
readings are only to be made to this degree of accuracy, this small error
is of no importance. The cistern is made of boxwood, which is sufficiently
porous to allow the atmosphere to influence the mercurial column; but the
top is plugged with porous cane, to admit of free and certain play.
=16. Admiral FitzRoy's Scale Words.=--The directions given on the scales
of these barometers were drawn up by Admiral FitzRoy, F.R.S. They appear
to be founded on the following considerations:--
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