A Barometer Manual for the Use of Seamen

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H.M. Stationery Office, 1884 - Weather forecasting - 41 pages
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Page 33 - ... storm is approaching, and travels more rapidly than the storm's center. The best and surest of all warnings, however, will be found in the barometer. In every case there is great barometric disturbance. Accordingly, if the barometer falls rapidly, or even if the regularity of its diurnal variation be interrupted, danger may be apprehended. No positive rule can be given as to the amount of depression to be expected, but at the center of some of the storms the barometer is said to stand fully 2...
Page 17 - Stand with your back to the wind, and the barometer will be lower on your left hand than on your right.
Page 2 - Then lift the instrument carefully out of its box, bend back the hinged part of the suspension arm, and slip it into the bracket. (The holding screws should not be driven quite home until the instrument is in position.) The mercury will then fall gradually, and the instrument will usually be ready for observation in about an hour.
Page 38 - Correction to be applied to Barometers with Brass Scales, extending from the Cistern to the top of the Mercurial Column, to reduce the observation to 32 Fahrenheit.
Page 33 - ... 50 nautical miles. As the center of the storm is approached the more rapid become the changes of wind, until at length, instead of its direction altering gradually, as is the case on first entering the storm field, the wind flies around at once to the opposite point, the sea meanwhile breaking into mountainous and confused heaps. There are many instances on record of the wind suddenly falling in the vortex and the clouds dispersing for a short interval, though the wind soon blows again with renewed...
Page 36 - NE., the center will probably be from S. to SSE. of the observer's position. However, it is difficult to estimate the center of the vortex from any given point. This partly arises from the uncertainty as to the relation between the bearing of the center and the direction of the wind, and greatly from there being no means of knowing whether the storm be of large or small dimensions. If the barometer falls slowly, and the weather grows worse only gradually, it is reasonable to suppose that the storm...
Page 32 - In all cases within the tropics, they commence to the eastward. For some days they travel along a path not exactly west, but inclining a point or two towards the...
Page 2 - It will be necessary, on returning the form when filled, to accompany it with the following data for reduction. A blank is left for this purpose on the back of the form. " The geographical co-ordinates of the place of observation, viz. latitude and longitude. " The altitude of the cistern of the barometer above the level of the sea, exactly ; if not, as near as it can be obtained. " The internal diameter of the tube of the barometer.
Page 36 - In the northern hemisphere, if in the right-hand semicircle, heave to on the starboard tack. If in the left-hand semicircle, run, keeping the wind if possible, on the starboard quarter, and when the barometer rises, if necessary to keep the ship from going too far from the proper course, heave to on the port tack. When the vessel lies in the direct line of advance of the...
Page 37 - ... remarked that in some cases a vessel may, if the storm be traveling slowly, sail from the dangerous semicircle across the front of the storm, and thus out of its influence. But as the rate at which the storm is traveling is quite uncertain, this is a hazardous proceeding, and before attempting to cross the seaman should hesitate and carefully consider all the circumstances of the case, observing particularly the rate at which the barometer is falling.

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