Thermometers For Engineers
1st. Salinometer.—Under the circumstances at which fresh water boils at 212°, sea water boils at 213°·2. The boiling temperature is raised by the chemical solution of any substance in the water, and the more with the increase of matter dissolved.
From a knowledge of this principle, marine engineers make use of the thermometer to determine the amount of salts held in solution by the water in the boilers of sea-going steamers. Common sea-water con
| Proportion of Salt in 100 parts of water | 0 | Boiling-point | 212° |
| "" | 1â„33 | " | 213·2 |
| "" | 2â„33 | " | 214·4 |
| "" | 3â„33 | " | 215·5 |
| "" | 4â„33 | " | 216·6 |
| "" | 5â„33 | " | 217·9 |
| "" | 6â„33 | " | 219·0 |
| "" | 7â„33 | " | 220·2 |
| "" | 8â„33 | " | 221·4 |
| "" | 9â„33 | " | 222·5 |
| "" | 10â„33 | " | 223·7 |
| "" | 11â„33 | " | 224·9 |
| "" | 12â„33 | " | 226·0 |
Fig. 74.
When the salts in solution amount to 12â„33, the water is saturated. It has also been ascertained that, when a solution of 4â„33 is attained, incrustation of the substances commences on the boiler. Hence, it is a rule with engineers to expel some of the boiling water, when the thermometer indicates a temperature of 216°, and introduce some more cold water, in order to prevent incrustation, which not only injures the boiler, but opposes the passage of heat to the water. The thermometer used for this purpose should be very accurately graduated, and the scale must be considerably higher than, though it need not read much below 212°.
2nd. Pressure Gauge.—The elasticity of gases augments by increase of temperature, and vice versa; it follows, therefore, that when steam is generated in a closed boiler, its temperature rises beyond the boiling temperature of 212°, owing to the increased pressure upon the water. The law connecting the pressure and the corresponding temperature of steam is the same as that upon which the boiling of fluids under diminished atmospheric pressure takes place. Hence, the indications of the thermometer become exponents of steam pressure. Engineers are furnished, in works on the steam-engine, with tables, from which the pressure corresponding to a given temperature, or the converse, can be obtained by mere inspection.
Fig. 74 represents the thermometer employed as a steam-pressure gauge. It is fitted in a brass case, with screw-plug and washers for closing the boiler when the thermometer is not in use. The scale shows the pressure corresponding to the temperature, from 15 to 120 lbs., above the atmospheric pressure, which is usually taken as 15 lbs. on the square inch.
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Negretti & Zambra&rsquos Second Patent Mercurial Minimum Thermometer
In this thermometer a principle is used that has been long known to scientific men, viz. the affinity of mercury for platinum. If mercury be placed in contact with platinum under ordinary circumstances, no effect will take place; but if the mercury... Negretti And Zambra&rsquos Farmer&rsquos Barometer And Domestic Weather-glass
<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
<div>Fig. 29.<br> <img src="/images/fig29.jpg" alt=""></div> <p><br> Fig. 29 is an illustration of the mountain barometer known as Newman’s. The cistern consists of two separate compartments;—the top of the lower and the bottom of the... On Sixe&rsquos Principle
Thermometers for ascertaining the temperature of the sea at various depths are constructed to register either the maximum or minimum temperature, or both. The principle of each instrument is that of Sixe. There are very few parts of the ocean in whi... Osler&rsquos Anemometer And Pluviometer
Mr. Follet Osler is the inventor of a self-recording apparatus which registers the direction and pressure of the wind, and the amount and duration of rain, upon the same sheet of paper. His apparatus has met with very much approbation, and has been... Phillip&rsquos Maximum Thermometer
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
Rain gauges should be placed on the ground, in any position exposed to a free fall of rain, snow, or hail, where neither walls, buildings, nor trees shelter or cause eddies of wind. They should be supported by a frame, or other means, to prevent the... Pouillet&rsquos Pyrheliometer
<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
<div>Fig. 1.<br> <img src="/images/fig1.jpg" alt=""></div> <p><br> The first instrument which gave the exact measure of the pressure of the atmosphere was invented by Torricelli, in 1643. It is constructed as follows:—A glass tube, CD (fig.... Regnault&rsquos Condenser Hygrometer
<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
<p>This barometer has been suggested to Messrs. Negretti and Zambra by Wentworth Erk, Esq. It consists of a regular barometer; but attached to the vernier is a double rack worked with one pinion, so that in setting or adjusting the vernier in one posi... Self-registering Rain-gauge
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
“As the interchange of heat between two bodies by radiation depends upon the relative temperature which they respectively possess, the earth, by the rays transmitted from the sun during the day, must be continually gaining an accession of heat... Standard Barometer
<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... Syphon With Photographic Registration
A continuous self-registering barometer has been constructed, in which photography is employed. Those who may wish to adopt a similar apparatus, or thoroughly to understand the arrangements and mode of observation, should consult the detailed descr... Temperature Is The Energy With Which Heat Affects Our Sensation Of Feeling
<p>Bodies are said to possess the same temperature, when the amounts of heat which they respectively contain act outwardly with the same intensity of transfer or absorption, producing in the one case the sensation of warmth, in the other that of coldn... The Barometer Vernier
The <em>vernier</em>, an invaluable contrivance for measuring small spaces, was invented by Peter Vernier, about the year 1630. The barometer scale is divided into inches and tenths. The vernier enables us to accurately subdivide the tenths into hun... The Common Formthe Barometer Is Of Great Use To The Mariner Who By Using It As A &ldquoweather Glass&rdquo Is Enabled To Fores
<p>Other forms of barometer (to be immediately described) have superseded this in the British Marine, but the French still give the preference to the wooden frames. They think the barometer can be more securely mounted in wood, is more portable, and l... The Fitzroy Marine Barometer
<p>Admiral FitzRoy deemed it desirable to construct a form of barometer as practically useful as possible for marine purposes. One that should be less delicate in structure than the Kew barometer, and not so finely graduated. One that could be set at ... The Kew Marine Barometer
The form of barometer so-called, is that recommended by the Congress of Brussels, held in 1853, for the purpose of devising a systematic plan of promoting meteorological observations at sea.</p> <p>The materials employed in its construction are mer... The Scale
The two fixed points having been determined, it is necessary to apply the scale. The thermometers in general use in the United Kingdom, the British Colonies, and North America are constructed with Fahrenheit’s scale. Fahrenheit was a philosoph... The Syphon Tube Mountain Barometer On Gay Lussac&rsquos Principle
The Syphon Tube Mountain Barometer, on Gay Lussac’s principle is fixed in a metallic tubular frame, forms a simple and light travelling instrument. The graduations are made upon the frame, and it is suspended for reading by a ring at the top, fr... The Vane
<div>Fig. 86.<br> <img src="/images/fig86.jpg" alt=""></div> <p><br> The instrument by which the wind’s direction is most generally noted, is the vane, or weather-cock, and all that need be said of it here is that the points north, east, s... The Words On The Scale
The following words are usually engraved on the scales of these barometers, although they are not now considered of so much importance as formerly:—</p> <table summary="table" border="0" cellpadding="0" cellspacing="5"> <tbody> <tr> ... Thermometer Screen For Use At Sea
This screen, or shade, was designed by Admiral FitzRoy, and has been in use for several years on board H.M. vessels and many merchant-ships. It is about twenty-four inches long by twelve wide and eight deep; having lattice-work sides, door, and bot... Thermometers For Engineers
<em>1st. Salinometer.</em>—Under the circumstances at which fresh water boils at 212°, sea water boils at 213°·2. The boiling temperature is raised by the chemical solution of any substance in the water, and the more with the increas... Thermometric Substances
Thermometers for meteorological and domestic purposes are constructed with liquids, and generally either mercury or alcohol, because their alterations of volume for the same change of temperature are greater than those of solids; while being more ma... Thomson&rsquos Electrometer
Professor W. Thomson, of Glasgow, has devised an atmospheric electrometer, which is likely to become eminently successful, in the hands of skilful observers. It is mainly a torsion balance combined with a Leyden-jar. The index is an aluminium needle... Trials Of The Fitzroy Marine Barometer Under Fire Of Guns
Some of the first barometers made by Messrs. Negretti and Zambra on Admiral FitzRoy’s principle were severely tried under the heaviest naval gun firing, on board H.M.S. <em>Excellent</em>; and under all the circumstances, they withstood the c... Use Of The Barometer In Estimating The Height Of Tides
The pressure of the atmosphere affects the height of the tide, the water being in general higher as the barometer is lower. The expressions of seamen, that “frost nips the tide,” and “fog nips the tide,” are explained by the ... Use Of The Barometer In The Management Of Mines
The inflammable and suffocating gases, known to coal-miners as fire-damp and choke-damp, are specifically heavier than air; and as they issue from the fissures of the mine, or are released from the coal, the atmospheric pressure tends to drive them... Vacuum Solar Radiation Thermometer
In order that the heat absorbed by the blackened bulb of the solar radiation thermometer may not in part be carried off by the currents of air which would come into contact with it, the instrument has been improved by Messrs. Negretti and Zambra int... Varieties Of Thermometers
<p>Fig. 37 is an illustration of boxwood scale thermometers for general use and common purposes.</p> <p>Fig. 38, Negretti and Zambra’s Travelling Thermometer; it is fixed in a plated metal (silver or otherwise) case, similar to a pencil-case, an... Whewell&rsquos Anemometer
This apparatus, the invention of the celebrated Dr. W. Whewell, registers the horizontal motion of the air with the direction. Its mechanism may be described in general terms, as follows:—</p> <p>A horizontal brass plate is attached to a ver... Athrioscope
The celebrated experimental philosopher, Sir John Leslie, was the inventor of this instrument, the purpose of which is to give a comparative idea of the radiation proceeding from the surface of the earth towards the sky. It consists, as represented... Public Barometers
<p>Since the increased attention paid to the signs of forthcoming weather of late years, and the good which has resulted therefrom to farmers, gardeners, civil engineers, miners, fishermen, and mariners generally, by forewarning of impending wet or sto...