Metallic Barometer
This instrument, the invention of M. Bourdon, has a great resemblance to the aneroid, but is much simpler in arrangement. The inventor has applied the same principle to the construction of metallic steam-pressure gauges. We are here, however, only concerned with it as constructed to indicate atmospheric pressure. It consists of a long slender flattened metallic tube, partially exhausted of air, and hermetically closed at each end, then fixed upon its centre, and bent round so as to make
This movement is augmented and transferred by a mechanical arrangement of small metallic levers to a radius bar, which carries a rack formed on the arc of its circle. This moves a pinion, upon the arbour of which a light pointer, or “hand,” is poised, which indicates the pressure upon a dial. When the pressure increases, the ends of the tube approach each other, and the pointer moves from left to right over the dial. The whole mechanism is fixed in a brass case, having a hole at the back for adjusting the instrument to the mercurial barometer by means of a key, which sets the pointer without affecting the levers. The dial is generally open to show the mechanism, and is protected by a glass, to which is fitted a moveable index.
This barometer is very sensitive, and has the advantage of occupying little space, although it has not yet been made so small as the aneroid. Both these instruments admit of a great variety of mounts to render them ornamental. The metallic barometer can be constructed with a small clock in its centre, so as to form a novel and beautiful drawing-room ornament.
Admiral FitzRoy writes, “Metallic barometers, by Bourdon, have not yet been tested in very moist, hot, or cold air for a sufficient time. They are dependent, or secondary instruments, and liable to deterioration. For limited employment, when sufficiently compared, they may be very useful, especially in a few cases of electrical changes, not foretold or shown by mercury, which these seem to indicate remarkably.”
They are not so well adapted for travellers, nor for measurements of considerable elevations, as aneroids.
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We have now to examine the construction of the boiling-point thermometer, and its necessary appendages, as adapted for the determination of heights.</p> <div>Fig. 72.<br> <img src="/images/fig72.jpg" alt=""></div> <div>Fig. 73.<br> <img src="... Nature Of Ozone
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<p>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 remo... Negretti And Zambra&rsquos Patent Maximum Thermometer
consists of a glass tube containing mercury fitted on an engraved scale, as shown in fig. 54. The part of the thermometer tube above the mercury is entirely free from air; and at the point A in the bend above the bulb, is inserted and fixed with th... Newman&rsquos Mountain Barometer
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A maximum thermometer, better perhaps in its action than Rutherford’s, has been suggested by Professor John Phillips, of Oxford. A small portion of air is introduced into an ordinary thermometer, so as to cut off about half an inch of the merc... Position For Rain-gauge &c
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<div>Fig. 67.<br> <img src="/images/fig67.jpg" alt=""></div> <p><br> This instrument is composed of a shallow cylinder of steel, <em>A</em>, fig. 67, which is filled with mercury. Into the cylinder a thermometer, <em>D</em>, is introduced, the ste... Precautions To Ensure Correct Graduation
Those who possess a boiling-point thermometer should satisfy themselves that it has been correctly graduated. To do this, it is advisable to verify it with the reading of a standard barometer reduced to 32° F. The table of “Vapour Tension&... Principle Of
If some mercury, or any other fluid, be poured into a tube of glass, bent in the form of <strong>∪</strong>, and open at both ends, it will rise to the same height in both limbs, the tube being held vertically. If mercury be poured in first, an... Principle Of The Barometer
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<div>Fig. 78.<br> <img src="/images/fig78.jpg" alt=""></div> <p><br> <p>(Fig. 78) consists of a tube, <em>C</em>, made of silver, very thin, and perfectly polished; the tube is larger at one end than the other, the large part being 1·8 inches i... Robinson&rsquos Anemometer
<em>Dr. Robinson</em>, of Armagh, is the inventor of a very successful anemometer, which determines the horizontal velocity of the wind. It was first used in 1850, in the meteorological and tidal observations made on the coast of Ireland under the d... Rules For Foretelling The Weather
<p><br> A RISING BAROMETER.</p> <div> <p>A “Rapid” rise indicates unsettled weather.</p> <p>A “Gradual” rise indicates settled weather.</p> <p>A “Rise,” with dry air, and cold increasing in summer, indicat... Self-compensating Standard Barometer
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The rain-gauge can be combined with clock-work and other mechanism so as to be self-recording of the amount of rain, the time, and duration of its fall. For the details of construction the reader is referred to the next chapter, where he will find t... Set Of Portable Instrument
<p>In a small box, 8 in. by 8 in. by 4 in., a complete set of meteorological instruments have been packed. The lid of the box, by an ingenious arrangement, is made to take off and hang up; on it are permanently fixed for observation, a maximum and min... Small Size Aneroids
The patent for the Aneroid having expired, Admiral FitzRoy urged upon Messrs. Negretti & Zambra the desirability of reducing the size at which it had hitherto been made, as well as of improving its mechanical arrangement, and compensation for te... Solar And Terrestrial Radiation Considered
The surface of the earth absorbs the heat of the sun during the day, and radiates heat into space during the night. The envelope of gases and vapour, which we call the atmosphere, exerts highly important functions upon these processes. Thanks to th... Solar Radiation Thermometer
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<p>Fig. 3 represents a Standard Barometer on Fortin’s principle. The barometer tube is enclosed and protected by a tube of brass extending throughout its whole length; the upper portion of the brass tube has two longitudinal openings opposite ea... Standard Syphon Barometer
<p>Fig. 24 represents the most accurate form of the Gay Lussac barometer. The short limb is closed at the top, after the mercury is introduced, and a small lateral), and here illustrated (fig. 25). Fig. 25.<br> <img src="/images/fig25.jpg" alt=""> ... Standard Thermometer
<div>Fig. 36<br> <img src="/images/fig36.jpg" alt=""><br> </div> <p>The peculiarities in the construction of thermometers will be best understood by describing the manufacture of a <em>Standard Thermometer</em>, which is one of the most accurate m... Sympiesometer
<div>Fig. 32.<br> <img src="/images/fig32.jpg" alt=""></div> <p>Nevertheless the instrument now about to be described, depending upon similar principles, but scientifically constructed and graduated, is a very useful and valuable substitute for the...