Barograph

“ A few of these instruments, such as the Marvin barograph, survived for some time because of their superior accuracy. Even as museum pieces, only a few exist today.
U.S. GOVERNMENT PRINTING OFFICE, 1961. ”

“ These figures, with our own tables of wind and flight pressures under all revolution speeds, give us approximately the exact rate of advance. He must watch and keep in operation the barograph or self-recording altitude gauge which takes the place of the usual barometer; as a check he also notes and records periodical readings of the regular barometer; he keeps constant watch on the car equilibrium by means of the statoscope; he records the compass course, sets down the latitude and longitude by following the compass bearing and the advance in miles ”

“ The semi-diurnal maxima and minima are greatest in equatorial latitudes; they decrease in higher atitudes. According to the observations of General Greely, the oscillations of the barograph pen were scarcely noticeable in polar regions. ”

“ The paper being carried steadily round on a drum at a given rate per hour, the height of the column of mercury is photographed continuously on the paper. From the photograph the height of the barometer at any instant may be taken. The principle of the aneroid barometer has been applied to the construction of barographs. The lever attached to the collapsible chamber terminates in an ink-fed style which records the pressure of the atmosphere on a moving ribbon. ”

“ It regulates the movements not only of our clocks, watches and chronometers, but of barographs, thermographs and a great variety of other machines for recording events and changes in their proper order and relation in respect to time. ”

“ But the vague prognostics of old times are not sufficient for the guidance of the skilful and provident farmer of our day. The barometer, the thermometer, and even the hygrometer, should be his companions and guides, or occasional counsellors. To the description and useful indications of these instruments, therefore, a sufficient space is devoted in the book before us. We do not know any other source from which the practical farmer can draw so much meteorological matter specially adapted to his own walk of life, as from this chapter upon the weather. ”

“ A steady rise in the barometer means a steady fall in the thermometer; a fall in the barometer in a time of great cold infallibly prophesies warmer weather; even such rapid changes as the one given above are anticipated. So well is this established, that during "50°-below spells" at Fairbanks, impatient, weather-bound travellers and freighters would busy the [56] hospital telephone with inquiries about the barometer, the hospital having the only barometer in the country. ”

“ If the amount of change in the pressure or of rise and fall of the barometer during the preceding night be plotted every morning on such a chart, it is found that the path of the system for the day does not lie directly toward the region where the greatest fall has occurred during the night, but is regulated to a certain extent by the direction of the line drawn from the point of greatest fall to that of greatest rise. ”

“ These are simply the highest and lowest readings of the barometer, usually designated maxima and minima, and should for the object in view receive particular attention. Whenever there is reason to believe that the barometer is approaching either a maximum or minimum, additional observations should be resorted to, so as to secure as nearly as possible the precise time as reckoned at the ship, with her position, of its occurrence, as well as the altitude of the mercurial column at that time and place. ”

“ Difficult as it is to foretell weather accurately, much useful foresight may be acquired by combining the indications of instruments (such as the barometer, thermometer, and hygrometer) with atmospheric [6] appearances. What is more varying than the aspect of the sky? Colour, tint of clouds, their soft or hard look, their outline, size, height, direction, all vary rapidly, yet each is significant. ”

“ Whatever the condition of the sky, whether clear or clouded, the Geotrupes announce fair weather or storm by their excited movements in the evening twilight. They are living barometers, more worthy of belief perhaps, in such contingencies, than the barometer of our scientists. The exquisite sensitiveness of life is mightier than the brute weight of a column of mercury. ”

“ The weather is a thing that is beyond me altogether. I never can understand it. The barometer is useless: it is as misleading as the newspaper forecast.
There was one hanging up in a hotel at Oxford at which I was staying last spring, and, when I got there, it was pointing to "set fair." It was simply pouring with rain outside, and had been all day; and I couldn't quite make matters out. I tapped the barometer, and it jumped up and pointed to "very dry." The Boots stopped as he was passing, and said he expected it meant to-morrow. ”

“ In order to discover the extent of this phenomenon, the hours of its recurrence, and the amplitude of the alternate rise and fall, the daily record of the barometer is carefully examined, and, whenever the phenomenon is found clearly defined, the hours of the two extreme lowest and two extreme highest readings, together with the readings themselves, are noted and tabulated on the blank. To save repetition, I will state here that all compilations of the barometer are reduced to 32° Fahr. and sea-level. ”

“ The barometer, by the sudden fall of its column of mercury, tells, as plainly and certainly as if it spoke with an audible voice, that a storm is approaching, even though all nature should appear to contradict the fact by its calm and serene aspect ”

“ With the principles of this science all the more reliable rules of weather-forecasting are most intimately connected. We no longer think of judging of coming weather merely by the aspect of the sky and an examination of an individual barometer. We invariably refer—I do not say to the weather-reports of a few hours previous, for we often have neither these nor any weather-reports at all at hand—but we invariably refer to rules already deduced from the long study of weather-maps. The man who ignores these rules had better, in my opinion, leave all attempts at weather-forecasting alone. ”

“ Taking the state of the barometer in connexion with the appearance of the weather one could make a satisfactory conclusion as to the quarter from which any violent wind would come. And the barometer, after very little practice, can be used by any man. There is no difficulty in using it sufficiently to know that danger is coming on; and if danger is coming on, a man refrains, of course, from exposing himself to it; the quarter from which the wind comes being of minor consequence. ”

“ We have generally found country folk more reliable about the immediate future of the weather than the falling or rising of the barometer, for local conditions are often an important factor in the case and modify the barometer’s forecast. ”

“ It will be requisite also, that the Observers give notice of the Scituation of the place, where their Barometers stand, not only, because it will assist men to Judge, whether the Instruments were duely perfected, but principally, because, that though the Baroscope be good (nay, because it is so) the Observations will much disagree, even when the Atmosphere is in the same state, as to Weight, if one of the Instruments stand in a considerably higher part of the Countrey, than the other. ”

“ The Barometer as a Weather-glass.—Generally speaking when the mercurial column in the barometer falls, ‘rain’ is indicated, and ‘fair weather’ when it rises. When it continues steady, a continuance of the weather at the time is regarded as the forecast; when low, the weather is generally broken or bad; and when high, it is fair and settled. A storm is usually preceded by a sudden fall in the mercurial column, the violence of the storm being in proportion to the suddenness of the fall. ”

“ In predicting the weather a great deal of use is made of an instrument called the barometer. The barometer shows how hard the air around it is pressing. If the air is pressing hard, the mercury in the barometer rises. If the air is not pressing hard the mercury sinks. Just before a storm, the air usually does not press so hard on things as at other times; so usually, just before a storm, the mercury in the barometer is lower than in clear weather. You will understand the barometer better after you make one. Here are the directions for making a barometer:
Experiment 87. ”

“ Readings must be taken at different intervals or the results will be misleading. The important thing about the barometer is to watch the rise and fall, particularly, whether it is gradual or rapid. From no single reading can you make an observation or a forecast. ”

“ To the great majority of observers any barometer scale is more or less empiric. By long training and habit one gradually acquires a mental value of the figures which express pressure and these become visual proportions that can be compared in the mind. ”

“ When we ascend a mountain we leave some portion of the atmosphere below us, and of course less remains above; this smaller quantity must have less weight and press the mercury less forcibly. If the barometer tells the truth, it must show this difference; and it does so with such accuracy that by means of a barometer, or rather of two barometers—one at the foot of the mountain and one at its summit—we may, by their difference, measure the height of the mountain provided we know the rules for making the requisite calculations. ”

“ It is a well-known fact that the barometer is as much, or even more affected by a change of wind as it is by rain; and the objection raised against a simple barometer reading, as leaving the observer in doubt whether to expect wind or rain, is removed by the addition of the Hygrometer, an instrument indicating the comparative degree of dryness or dampness of the air;—a most important item in the determination of the coming weather. ”

“ So a fall in the barometer precedes the coming of a high wind or a rainstorm. A rise in the barometer precedes a calm, and since most rain is accompanied with wind, the calm is a time of fair weather. ”

“ Every day there is a weather map made up showing the locations of the high and low barometers, direction of wind, lines of equal pressure, as well as those of temperature. By study from year to year all of these phenomena have become systematized, so that by tracing an area of low barometer from its origin in its progress easterly it is soon seen to fall under one of these classes and we are able to predict about what its course will be. ”

“ In examining the barometer for the purpose of forecasting the weather, the position of the mercury during previous days or hours should not be neglected, for an indication at any particular moment may be affected by causes operating at a distance and not visible to the observer whose barometer feels their effect. ”

“ As mankind are always desirous of attaining weather wisdom, these rules have tended to give the barometer its widely recognized reputation, rather than any really infallible principles, clearly formulated. With no other philosophical instrument have people so deluded themselves as with the barometer. Meteorology having become almost an official monopoly, the officials seem to have made the readiest and largest amount of reputation out of the barometer as a weather glass ”

“ A study of the edition, "Coast or Fishery Barometer Manual," teaches that the barometer foretells coming weather; that it does not always foretell coming weather; that only few are able to understand much about what it does tell us; that it may be used by ordinary persons without difficulty; that its indications are sometimes erroneous: that any one observing it once a day may be always weatherwise; that its warnings do not apply always to the locality of the instrument; that storms frequently occur without its giving any warning; that barometer depressions happen with and without gales ”

“ Each observation of the barometer should be accompanied by an observation of the wind—its direction should be most carefully noted, and the force estimated according to the scale in page 21, or by the anemometer. It would be as well at the time to project the barometric readings in a curve even of a rough character, that the extent of fall after the mercury had passed its maximum might be readily discernible by the eye. ”

“ The seasons affect the barometer, it is true. A sudden fall of the barometer in the autumn or in the spring indicates wind; in the summer or in hot weather it prognosticates a thunderstorm; in winter, after frost, a sudden fall of the mercury shows a change of wind or a thaw with rain; but in a continued frost a rise of mercury indicates approaching snow. ”

“ Familiar as the practical use of weather-glasses is, at sea as well as on land, only those who have long watched their indications, and compared them carefully, are really able to conclude more than that the rising glass [3] USUALLY foretells less wind or rain, a falling barometer more rain or wind, or both; a high one fine weather, and a low, the contrary. ”

“ The scientific prediction of the weather by means of the barometer involves the comparison of the simultaneous readings of barometers over as wide an area as possible, and can only be carried out where there is a complete telegraph system and a public department charged with the work. ”

“ If, on the contrary, during a rainy period which has already had a long duration, the barometer commences to rise slowly and regularly, very certainly fine weather will come, and it will last much longer if a long interval elapses between its arrival and the rising of the barometer. ”

“ High-class instruments, such as that here described, yield exact readings; but, in order to note them accurately, it is important that the eye, the zero edge of the vernier, the top of the mercurial column, and the back of the vernier should be in the same horizontal plane; conditions which may be obtained after some practice.
The accompanying illustration shows a form of barometer which, though not much used in this country, is deservedly popular on the Continent as a standard station barometer. ”