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parent body, which freely admitted the rays of light to pass through it, stopping the calorific rays; but that caloric was not entirely intercepted, is evident from the circumstance of the thermometer not falling below 5°.7. Another proof that the calorific rays exist independently of the luminous ones is, that the same results took place when a flask of boiling water was used instead of the candle. When a concave mirror of glass was substituted in place of the metallic reflector, little effect was produced upon the thermometer; thus proving the inferiority of glass as a reflector of heat.

M. Pictet endeavoured to ascertain the velocity with which the calorific rays moved, and for this purpose he placed the reflectors at a distance of sixty-nine feet from each other, having in the one focus a heated ball, and in the other a delicate air thermometer. A cloth screen was interposed between the reflectors, upon the removal of which the rise of the thermometer was instantaneous; so that, within this distance, no perceptible interval elapsed between the passage of the calorific rays from one point to the other.

Absorption, as applied to caloric, implies that power which substances possess, of retaining the heating rays which impinge upon them,' and thereby of acquiring an elevation of temperature. The absorptive powers of substances are very different, and may be roughly said to vary directly as the power of radiation. As far as the calorific effect of the sun-beam is concerned, it has been shewn, that the power of the absorbent body greatly depends upon its colour.

Mr. Powell, who has written several papers on the nature of caloric in the Philosophical Transactions, has thus stated his views on the subject.

1. "That part of the heating effect of a luminous hot body, which is capable of being transmitted in the way of direct radi. ation through glass, affects bodies in proportion to their darkness of colour, without

reference to the texture of their surfaces.

2. "That which is intercepted produces a greater effect in proportion to the absorptive nature or texture of the surface, without respect to colour. These two characteristics are those which distinguish simple radiant heat at all intensities.

"Thus, when a body is heated at lower temperatures, it gives off only radiant heat, stopped entirely by the most transparent glass, and acting more on an absorptive white surface than on a smooth black one.

"At higher temperatures the body still continues to give out radiant heat, possessing exactly the same characters. But at a certain

point it begins to give out light: precisely at this point, it begins also to exercise another heating power, distinct from the former; a power which is capable of passing directly through transparent screens, and which acts more upon a smooth black surface than on an absorptive white one."

It seems to be the general tendency of caloric, to become so diffused among matter of every kind, as to produce uniformity of temperature. That bodies differ greatly in the facility with which they permit the motion of caloric, or transmit its effects, is matter of daily observation. The transmission of caloric in free space, or through aeriform fluids, seems to be instantaneous, but in solids and liquids the case is very different. It may be stated as a general fact, that the conducting power of any body is in proportion to its density; thus, metals are better conductors than glass, glass than wood, and wood than feathers, wool, and other light substances, &c. The bad conducting power of these latter bodies, depends upon the quantity of air enclosed within their interstices, and the force of attraction by which this air is confined. If their imperfect conducting power depended on the difficulty with which caloric passes through their solid matter, the relative degree of that power would be as to the quantity of that matter. The reverse, however, is the case. Thus, the reason is evident, why wool, down, furs, &c. form such warm articles of clothing; because, in the ordinary state in which they are employed, the effect of their own bad-conducting property, and that of the air retained in their interstices, prevents the abstraction of caloric from the body. From its porous nature, snow is a very bad conductor, and thus forms an admirable mantle for the protection of vegetables from the more intense cold of winter.

The

As liquids are very easily heated, it may at first sight appear that their conducting power is considerable. The very opposite is, however, the true state of the case. mobility of their particles is the chief cause of their power of transmitting heat, as may be seen from attending to the manner in which caloric acts upon them. If heat be applied to the lowest surface of any vessel containing a liquid, the first effect produced will be the expansion of the particles immediately in contact, by which their specific gravity being diminished, they will ascend through the mass of fluid, and a fresh stratum of particles will descend to occupy their place. By a repetition of this process, the whole body of fluid soon becomes heated. But if heat be applied to the upper

surface of a liquid, no such effect can take place; the heated and lighter particles continue at the surface; and the caloric, if it proceed downwards at all, will do so very slowly, and must do so on the principle of absorption.

Count Rumford exemplified this carrying power of liquids by a very pleasing experiment. He made a solution of potash and water of the same specific gravity with amber; then strewing in it some roughly powdered amber, he enclosed the whole in a proper glass vessel, and, after exposing it to a considerable heat, placed it in a window to cool. As the sun shone upon the vessel, it illuminated the particles of amber, and the whole liquid was seen to be in most rapid motion, running swiftly in opposite directions, upwards and downwards at the same time. The ascending current occupied the axis, the descending current the sides of the vessel. When the sides of the vessel were cooled by means of ice, the velocity of both currents was accelerated. It diminished as the liquid cooled; and when it had acquired the temperature of the room, the motion ceased altogether. These currents were evidently produced by the particles of the liquid going individually to the sides of the vessel, and giving out their caloric. The moment they did so, their specific gravity being increased, they fell to the bottom, and of course pushed up the warmer part of the fluid, and so on in continuity. Count Rumford likewise found, that, by mixing a small quantity of starch with the water, so as to diminish the fluidity, it took nearly double the time to reach a certain temperature, that it did when pure water was used. Eider down was likewise mixed with water, which could only tend to embarrass the motion of the particles, and a rather more powerful effect was speedily produced.

It is principally by the agency of fluids, elastic and non-elastic, that the distribution of caloric over the globe is regulated, and great inequlaities of temperature are guarded against; and this agency is exerted chiefly by the circulation of which their mobility renders them susceptible.

Thus, the atmosphere, with which the earth is surrounded, serves the important purpose of moderating the extremes of temperature in every climate. When the earth is heated by the sun's rays, the stratum of air reposing on it receives part of its caloric, is rarefied, and ascends. At the same time, from a law which attends the rarefaction of elastic fluids, that they become capable of containing a greater quantity of caloric at a given temperature, as they become more

rare; this heated air, though its temperature falls as it ascends, retains the greater part of its heat; its place at the surface is supplied by colder air, pressing in from every side; and by this constant succession, the heat is moderated, that would otherwise become intense. The heated air is, by the pressure of the constantly ascending portions, forced towards a colder climate; as it descends to supply the equilibrium, it gives out the heat it had received, and this serves to moderate the extremes of cold. There thus flows a current from the poles towards the equator, at the surface of the earth, and another superior current from the equator to the poles; and though the directions of these are variously changed, by irregularities in the earth's surface, they can never be interrupted, but, produced by general causes, must always operate, and preserve, with greater uniformity, the temperature of the globe.

Water is not less useful in this respect in the economy of nature. When a current of cold air passes over the surface of a large collection of water, it receives from it a quantity of caloric; the specific gravity of the water is increased, and the cooled portion sinks. Its descent forces up a portion of warmer water to the surface, which again communicates a quantity of caloric to the air passing over it; and this process may be continued for a considerable time, proportioned to the depth of the water. If this is not very considerable, the whole is at length cooled to 40°, below which, the specific gravity not increasing, the circulation ceases, and the surface is at length so far cooled as to be covered with a coat of ice.

The quantity of caloric afforded by water is exceedingly great. Count Rumford says, "the heat given off to the air by each superficial foot of water, in cooling one degree, is sufficient to heat an incumbent stratum of air forty-four times as thick as the depth of the water, ten degrees. Hence, we see how very powerfully the water of the ocean, which is never frozen over except in very high latitudes, must contribute to warm the cold air which flows in from the polar regions." From this cause, currents must exist in the ocean similar to those formed in the atmosphere. The water, which in the colder regions is cooled at the surface, descends, and, spreading on the bottom of the sea, flows towards the equator, which must produce a current at the surface in the opposite direction; and thus the ocean may be useful in moderating the excessive heats of the torrid zone, as well as in obviating the intense cold of the polar climates.

ON THE CONIC PROJECTION OF THE SPHERE.

Of the several methods of projecting the surface of the earth, or of a sphere, on a plane, the globular is most esteemed, as giving the most faithful and correct representation of its surface, exhibiting it with equidistant meridians and parallels; it is, therefore, preferable to the other methods, because the different countries, &c. are represented more proportional to their dimensions as they stand on the globe.

If, however, a cone be inscribed in a hemisphere, and the various circles, lines, &c. as also the different continents and islands on its surface, be transferred to the convex surface of the cone; this will be a nearer approximation to the surface of a sphere than the globular projection, or than any other projection on a plane surface. Two such cones, so placed that their bases may coincide with the equator, and their axes with the axes of the sphere, will represent the whole surface of the earth, or the northern and southern hemisphere.

If the surfaces of each of these cones be unwound, they will present two plane surfaces, or great segments of circles, whose semidiameters are the slant heights of the cones; and if they be placed so that the chords of the arcs may coincide, the four sides of the sectors, or semidiameters of the circles, will form a rhombus, or diamond square, in the middle of the figure, in which the name of the map or other particulars may be written.

Such a map may be constructed as follows:

To find the length of the arc of the sectors; suppose the diameter of the circle to be 1, then the slant height of the cone will be 5, hence, by Euclid, 47th P. of .353 is the semidiameter

.5

2

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B. I√ of the base of the cone, and .353 × 2 × 3.1416 2.217 the length of the arc: now as 3.1416: 360°:: 2.217: 254° 9= length of the arc in degrees, and 360° 254°,, 91⁄2 105′,, 50' the length of the deficient arc. Therefore, with any radius draw a circle, cut off from the proper side of it 105° 50', next draw the two radii or sides of the sector; then, with the length of the radius from the points of section, describe arcs intersecting one another on the outside of the sectors; from the points where they intersect, circumscribe the arc of the other sector, meeting, or cutting the former; and then finish the rhombus, by drawing the sides of the sector.

Divide each of the arcs into 360 degrees for the longitude, and at proper distances

2D. SERIES.-NO. 6.

draw straight lines from the centre to the circumference, for meridian lines. The degrees of latitude must be marked on the sides of the rhombus; but as they are not of equal length, the points of division may be found as follows:-make the sides of the rhombus, chords of the arcs of quadrants, divide each of the arcs into 90 degrees, and through the points of division, to the vertex of each quadrant, draw straight lines, and the points where they cut the chords or sides of the rhombus, are the points of division for the degrees of latitude.

These divisious may be found arithmetically as follows:-there are given the base of a triangle, or radius of the quadrant, and both the angles at the base, and, therefore, that at the vertex, to find one of the sides, one angle at the base being the given latitude, and the other always 45°; hence, the sine of the angle at the vertex, is to the base or radius, as the sine of the latitude is to the required side or part of the chord corresponding to the given latitude. When the divisions of the latitude are found, arcs must be drawn through them, parallel to the equator, for the parallels of latitude, at proper distances from each other.

Thus much for maps of the world; but for maps of any part of the earth's surface, either in the northern or southern hemisphere:-in order to obtain the nearest approximation to the surface of a sphere, the surface of the spherical zone, lying in the latitude of the map, should be transferred to the surface of the frustrum of a cone, the semidiameters of whose greater and lesser bases, are the cosines of the latitudes of the bottom and top of the map. Let S,s, be the sines of the latitudes of the top and bottom of the map, and c, C, their cosines;

then C-c2 + S-s = the slant height of the frustrum, and by sine ▲s, as C C-c: √ C-c2 + S :: C: C-c

+

2

the slant height

of the whole cone or radius of the greatest parallel of latitude, whose length is 3.1416 x 2 C, a proportional part of which must be taken for the width of the map. The divisions of the degrees of latitude may be found by the former trigonometrical analogy, observing that the given base, or side of the triangle, is equal to the radius of the sphere, in the zone of which the frustrum of the cone was supposed to be inscribed, and one of the angles at the base being the difference of the latitude of the bottom of the map, and the given latitude whose distance

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is sought, and the other angle at the base is the given latitude, together with the angle whose sine is proportional to S-s. Or the divisions may be found geometrically with great ease.

Maps constructed in the above method will represent the different countries, &c. more proportional to their size; therefore, greater measurements may be performed with more correctness; and if celestial maps were thus constructed, they would, when properly bent, have the property of discovering the stars.

THOMAS COOKE.

Draycott, near Derby.

A SIMPLE BAROMETER.

MR. EDITOR, SIR, OBSERVING in your excellent periodical, vol. 3d, col. 830, an account of the leech being used as a barometer, I would beg leave to state, with due deference to your correspondent's observations, that it should be the horse-leech found in ponds or stagnant pools, instead of that used for medical purposes, the one being much stronger than the other, and more susceptible of acute feeling under the different changes of the atmosphere. But although it may be amusing to observe how the animal is affected by the weather, for my own part I have never found that degree of certainty attached to it which I could have wished. The most simple, cheap, and correct barometer, applicable to any useful purpose, is the following:

Take a common phial bottle; cut off the rim and part of the neck. This may be done by a piece of string, or rather whipcord, twisted round it, and pulled strongly by two persons in a sawing position, one of whom holds the bottle firmly in his left hand. Heated in a few minutes by the friction of the string, and then dipped suddenly into cold water, the bottle will be decapitated more easily than by any other means. Let the phial be now nearly filled with pump water; applying the finger to the mouth, turn it quickly upside-down; on removing the finger, it will be found that only a few drops escape. Without cork or stopper of any kind, the water will be retained within the bottle by the pressure of the external air, the weight of air without the phial being so much greater than the small quantity within it. Now, let a piece of tape be tied round the middle of the bottle, to which the two ends of a string may be attached, so as to form a loop to hang it on a nail. Let it be thus suspended in a perpendicular manner, with the

mouth open downwards, and this is the barometer.

When the weather is fair, and inclined to to be so, the water will be level with the section of the neck, or rather elevated above it, forming a beautiful concave surfacewhen disposed to be wet, a drop will appear at the mouth, which will enlarge till it fall, and then another drop, while the hunnidity of the atmosphere continues. The degree of certainty in this instrument may be relied upon, as I have used it for many years, and never found it fail in indicating the same change of weather with the common barometer. F. H. Leadenhall Street March 14, 1831.

ORIGIN OF THE ENGLISH LANGUAGE.

FROM the Anglo-Saxons we derive the names of the most ancient officers among us-of the greater part of the divisions of the kingdom, and of almost all our towns and villages. From them we derive our language; of which the structure, and a majority of its words, much greater than those who have not thought on the subject would at first easily believe, are Saxon.

Of sixty-nine words, which make up the Lord's Prayer, there are only five not Saxon; the best example of the natural bent of our language, and of the words apt to be chosen by those who speak and write it without design. Of eighty-one words in the soliloquy of Hamlet, thirteen only are of Latin origin. Even in a passage of ninety words in Milton, whose dic'ion is more learned than that of any other poet, there are only sixteen Latin words. In four verses of the authorized version of Genesis, which contain about a hundred and thirty words, there are no more than five Latin. In seventy-nine words of Addison, whose perfect taste preserved him from a pedantic or constrained preference for any portion of the language, we find only fifteen Latin. In later times the language has rebelled against the bad taste of those otherwise vigorous writers, who, instead of ennobling their style like Milton, by the position and combination of words, have tried to raise it by unusual and far-fetched expressions. Dr. Johnson himself, from whose corruptions English style is only recovering, in eighty-seven words of his fine parallel between Dryden and Pope, has found means to introduce no more than twenty-one of Latin derivation.-The language of familiar intercourse, the terms of jest and pleasantry, and those of necessary business, the idioms or peculiar phrases into which words naturally run, the proverbs, which are the condensed and pointed sense

of the people, the particles, on which our Syntax depends, and which are of perpetual recurrence;-all these foundations of a language are more decisive proofs of the Saxon origin of ours, than even the great majority of Saxon words in writing, and the still greater majority in speaking.

In all cases where we have preserved a whole family of words, the superior significancy of a Saxon over a Latin term is most remarkable. "Well-being arises from welldoing," is a Saxon phrase, which may be thus rendered into the Latin part of the language :-" Felicity attends virtue;" but how inferior in force is the latter! In the Saxon phrase, the parts or roots of words being significant in our language, and familiar to our eyes and ears, throw their whole meaning into the compounds and derivations, while the Latin words of the same import, having their roots and elements in a foreign language, carry only a conventional signification to an English ear. It must not be a subject of wonder that language should have any closer connexion with the thoughts and feelings which it denotes, than our philosophy can always explain. As words convey these elements of the character of each particular mind, so the structure and idioms of a language, those properties of which, being known to us only by their effect, we are obliged to call its spirit and genius, seem to represent the character or assemblage of quality which distinguish one people from others.-Lardner's Cabinet Cyclopedia.

ANNIVERSARIES OF BENEVOLENT INSTI

TUTIONS IN THE METROPOLIS.

WHEN the tide of benevolence first began to flow, many persons who watched its progress, hesitated not to predict that it was nothing more than a momentary effervescence, which would speedily expend its energy, and subside. Time, however, has proved, that false prophets may exist, without taking shelter under the sanction of religion. Instead of diminishing, these societies increase in number; instead of having expended their energies, they acquire renewed vigour; instead of contracting their spheres of operation, they occupy a wider field, embrace new objects, and every year their supporters become more

numerous.

Amounting in their varied forms to about one hundred, we must content ourselves with noticing some of the principal; for beyond this, our limits will not allow us to pass. To such of our readers, however, as wish to obtain an extended outline of

the speeches delivered at these anniversaries, we recommend the Christian Advocate Newspaper, as containing a faithful report of the transactions and sentiments which it records. The first in order that comes under our notice is the

ANTI-SLAVERY SOCIETY.

The anniversary of this truly benevolent institution was held at Exeter Hall, (a large and commodious room lately opened in the Strand, near Waterloo Bridge,) on Saturday, April 23. On this occasion his Royal Highness the Duke of Gloucester was expected to take the chair, but having been prevented through indisposition, Lord Suffield was called on to fill his place. His Lordship's address was manly, animated, and unequivocal. It breathed hostility to slavery in all its forms, and from the inhumanities inseparable from the system, still practised in our colonies, his Lordship argued the necessity of a total abolition.

T. Fowel Buxton, Esq., M. P. drew a frightful picture of this colonial monster, establishing his general view by an appeal to facts, some of which consign to the gibbet of infamy a clergyman of Jamaica, named Brydges, for his inhumanity towards one of his slaves. This detestable system, he asserted, has within a few years destroyed no less than forty-five thousand human beings.

Sir James Mackintosh argued forcibly on the necessity of a total abolition. Little had yet been done; but from the new Parliament, about to be returned, much might be expected.

Dr. Lushington avowed himself to be an advocate for the immediate and entire emancipation of West India slaves. Of every candidate soliciting to be returned to Parliament, he recommended that each voter should ask the question-do you abhor slavery? will you vote for its extermination?" and unless his answer prompt and unequivocal, to vote against him.

was

The Rev. Daniel Wilson was an enemy to slavery on religious grounds, and was resolved to co-operate in any measures that should tend to annihilate the horrid system.

Daniel O'Connell, Esq. M. P. declared himself the mortal foe of slavery, abhorring it in all colours, creeds, and climes. He asserted, that in fourteen colonies, during only ten years, there had been a decrease in population of forty-five thousand eight hundred and one. Every day ten human beings are despatched by slavery. It could be borne no longer, and he was resolved

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