its channel down to the furface of the rock, and between fix and feven feet wide, but in times of floods extended itself entirely over the valley. Researches have been made for the gold, amidst the fand and gravel along the run of the brook, for near half a mile in length; but it is only about one hundred and fifty yards above, and about two hundred yards below the ford, that the trials have been attended with much fuccess: within that space, the valley is tolerably level, and the banks of the brook have not more than five feet of fand and gravel above the rock; added to this, it takes a small turn to the fouthward, and, confequently, the rude furfaces of the thistus rock in fome degree cross its course, and form natural impediments to the particles of gold being carried further down the stream, which still lower has a more rapid defcent; befides, the rude manner in which the country people worked, seldom enabled them to penetrate to the rock, in those places where the fand and gravel were of any material depth. Their method was, to turn the course of the water wherever they deemed neceffary, and then, with any inftruments they could procure, to dig holes down to the rock, and by washing, in bowls and fieves, the fand and gravel they threw out, to separate the particles of gold which it contained; and from the flovenly and bafty way in which their operations were performed, much gold moft probably escaped their search; and that indeed actually appears to have been the cafe, for fince the late rains washed the clay and gravel which had been thrown up, gold has been found lying on the furface. The situation of the place, and the constant command of water, do, however, very clearly point out the great facility with which the gold might be separated from the trath, by adopting the mode of working practifed at the best managed tin stream works in the county of Cornwall; that is, entirely to remove (by machinery) the whole cover off the rock, and then wash it in proper buddles and fieves. And by thus continuing the operations, conftantly advancing in the ravine towards the mountain, as long as gold should be found, the vein that forms its matrix might probably be laid bare. 1 The discovery was made public, and the workings began, early in the month of September last, andcontinued till the 13th of October, when a party of the Kildare militia arrived, and took poffeffion by order of government; and the great concourse of people, who were bufily engaged in endeavouring to procure a share of the treafure, immediately defitted from their labour, and peaceably retired. Calculations have been made, that during the foregoing period, gold to the amount of three thoufand pounds Irish sterling was fold to various persons; the average price was three pounds fifteen shillings per ounce; hence eight hundred ounces appear to have been collected within the short space of fix weeks. The gold is of a bright yellow colour, perfectly malleable; the specific gravity of an apparently clean piece 19,000. A fpecimen, atlayed here by Mr. Weaver, in the moist way, produced from 24 grains, TOT grains, 22 grains of pure gold, and 1 of filver. Some of the gold is intimately blended with, and adherent to quartz; some (it is faid) was found united to the fine grained iron stone, but the major part was entirely free from the matrix; every piece more or less rounded on the edges, of various weights, forms, and fizes, from the most minute particles up to 2 oz. 17 dwt.; only two pieces are known to have been found of superior weight, and one of those is 5, and the other 22 ounces. Molesworth, Efq. F. R. S. writes, that he weighed the largest piece of gold in his balance, both in air and water; that its weight was 20 oz. 2 dwt. 21 gr. and its specific gravity, to that of sterling gold, as 12 to 18. Also that Richard Kirwan, Esq. F. R. S. found the specific gravity of another spcimen to be as 13 to 18. Hence, as the gold was worth £ 4 an ounce, Mr. William Molesworth concludes that the specimens are full of pores and cavities, which increase their bulk, and that there are some extraneous substances, such as dirt or clay, contained in those cavities. through some of the small lumps. I much regret not having been present when the work was going on, that I might have seen the gold as found, before prepared for fale by This opinion was discovered to breaking off any extraneous matter, be well founded, by cutting that adhered; for in that state, a proper attention to the substances with which it was united, and a subsequent diligent inspection of the several veins that range through the mountain, might affift towards the discovery of that from whence it was detached. I shall shortly return to England; and on my arrival, will fend fpecimens of the gold, and of the different substances of the moun tain, to be deposited (if you think And am, with great respect, &c. The bearings are all taken by the compass, without allowing for the variation. BESIDES these accounts of the gold found in Ireland, the following information has been received on that subject. William Molesworth, Esq. of Dublin, in a letter to Richard 1 STANESBY ALCHORNE, Esq. his majesty's assay-master at the Tower of London, assayed two specimens of this native gold. The first appeared to contain, in 24 carats, 21 of fine gold; of fine filver ; 1 of alloy, which seemed to be copper tinged with a little iron... The second specimen differed only in holding 21 instead of 218 of fine gold. Major John Brown, of the royal engineers, tranfmitted to the right hon. Thomas Pelham, a sketch of the spot where the gold was found, which Mr. Pelham has obligingly permitted to be engraved, for the ufe of the royal society. C. B. we should feel the fame degree of cold in all regions, after we have risen to a certain height, say 24,000 feet; confidering that the variations with respect to heat, on the earth, not only in the different climates, but in the fame country, at diffe. rent feasons of the year, are fo perceptible. This variety, which takes place at the furface of the globe, is undoubtedly occafioned by the fun. It appears, at first fight, that his influence must be the fame aboye and below, especially when we reflect, that a height of 24,000 feet, or a mile, though very great with refpect to us, and even far beyond the height of the loftieft mountains, is a mere nothing, com. pared to the distance of the fun. which is about thirty millions of miles*. This is therefore, a very important difficulty, which we muft endeavour to folve. For this purpose I begin with remarking, that the rays of the fun do not communicate heat to any bodies, but-such as do not grant them a free paffage. You know that bodies, through which we can difcern objects, are denominated tranfparent, pellucid, and diaphonous. These bodies are glass, crystal, diamond, water, and feveral other liquids, though fome are more or leis transparent than others. One of these tranfparent bodies being exposed to the fun, is not heated to fuch a degree as a body not tranfparent, as wood, iron, &c. Bodies not transparent are denominated opaque. A burning-glass, for example, by tranfmitting the rays of the fun, fets on fire opaque bodies, while the glass itself is not fenfibly heated. Water exposed to the fun becomes fomewhat warm, only because it is not perfectly tranfparent; when we fee it confiderably heated by the fun at the brink of rivers, it is because the bottom, being an opaque body, is heated by the rays which the water tranfmits. Now, every heated body commu-. nicates that heat to all adjoining bodies; the water accordingly derives heat from the bottom. If the water be very deep, fo that the rays cannot penetrate to the bottom, it has no preceptible heat, though the fun bears upon it, As air is a very transparent body, to a much higher degree than glass or water, it follows, that it cannot be heated by the fun, because the rays are freely tranfmitted through it. The heat which we frequently feel in the air, is communicated to it by opaque bodies, which the rays of the fun have heated; and were it poffible to annihilate all these bodies, the air would scarcely undergo any change in its temperature by the rays of the fun: exposed ta it or not, it would be equally cold. But the atmosphere is not perfectly transparent: it is even sometimes so loaded with vapours, that it loses almost entirely its tranfparency, and presents only a thick fog. When the air is in this state, the rays of the fun have a more powerful influence upon it, and heat it immediately. But these vapours rife to no great height; at the height of 24,000 feet, and beyond, the air is fo fubtile and fo pure, that it is perfectly transparent; and for this" reason the rays of the fun cannot immediately produce any effect upon it. This air is likewise too remote Mr. Euler always means German miles, of 4000 fathoms each, or fomewhat under 44 miles English.-E. E. remote from terreftrial bodies, to receive a communication of heat from them; they act only upon such as are adjacent. Hence you will eafily perceive, that the rays of the fun cannot produce any effect in regions of the air very much elevated above the furface of the earth; and that the fame degree of cold must always, and universally, prevail in such regions, as the fun has no influence there, and as the heat of terreftrial bodies cannot be communicated fo far. This is nearly the cafe on the fummit of very high mountains, where it is always much colder than on plains and in vallies *. The city of Quito, in Peru, is almost under the equator, and were we to form our judgment from its fituation on the globe, we would fuppofe it oppreffed with intolerable heat; the air, however, is abundantly temperate, and differs very little from that of Paris. Quito is fituated at a great height above the real furface of the earth. In going to it from the fea shore, you have to afcend for feveral days; it is accordingly built in an elevation equal to that of our highest mountains, though furrounded by others still much higher, called the Cordeliers. This last circumstance would afford a reason for thinking, that the air there must be as hot as at the furface of the earth, as it is contiguous, on all fides, to opaque bodies, on which the rays of the fun fall. The objection is folid; and no folution can be given but this. That the air at Quito, be ing very elevated, must be much more fubtile, and of less gravity than with us; and the barometer, which always stands confiderably lower, inconteftably proves it. Air of fuch a quality is not fo fufceptible of heat as common air, as it must contain less vapour and other particles which usually float in the atmosphere; and we know by experience, that air, very much loaded, is proportionably fufceptible of heat. I must here fubjoin another phenomenon, no less furprizing: In very deep pits, and lower ftill, if it were still poffible to defcend, the fame degree of heat always, and univerfally, prevails, and nearly for the fame reafon. As the rays of the fun exert their influence only on the furface of the earth, and as the heat which they there excite communicates itfelf up and down, this effect, at very great depths, is almost imperceptible. The fame thing holds respecting confiderable heights. This elucidation will, I flatter myfelf, prove fatisfactoryt. : Account * There are clouds, however, above these mountains, and in almost as great a quantity as above the plains, which is demonftrated by the fhows which cover the highest fummits. There are few naturalifts who have not been furprized by clouds in their excurfions upon the mountains. The heat that is felt when fuch clouds are formed, muft be attributed almost entirely to the tranfmiflion of the water which found itself diffolved in the air, under the form of elastic fluid, to a liquid ftate. The heat of the folar rays, intercepted by the cloud, can produce no change in the inferior temperature, as it would have been tranfmitted from the ground.-F. E. + The reafon which profeffor Euler affigns for the cold that prevails in the higher regions of the atmosphere frems plautible, but will not stand an accurate xamination. Light is much impaired in its passage through the atmosphere, Cc4 and Account of the Great Speckled Diver or Loon. From White's Naturalifts Calendar. AS one of my neighbours was traversing Wolmer forest from Bramshot across the moors, he found and the heat communicated is in every case proportional to the quantity of absorption. It appears, from fome ingenious experiments of M. Bouguer, that we receive only four-fifths of the rays of a vertical fun; and when that luminary ap. proaches the horizon, the portion of this light, which reaches the furface of the earth, is much smaller. Thus, at an elevation of 20 degrees, it is one-half, at that of 10 degrees, one-third; and at that of five degrees, one-eighth. Hence, the fun-beams are most powerful on the summits of lofty mountains, for they fuf. fer the greatest diminution in paffing through the dense air of the lower regions. If the air derived its heat from the furface of the earth, those countries would be warmest which enjoyed the greatest quantity of fun-shine. The British islands are shrouded in clouds nine months of the year; yet our climate is milder than that of the fame parallel on the continent, where the sky is generally ferene. The elevated town of Quito, exposed to a brilliant fun, enjoys a temperate air; while the Peruvian plains, shaded with fleecy clouds, are parched with heat. Were the reasoning in the text to be admitted, we should conclude, that the tops of mountains are warmer than their basis. To say that air, much rarefied, is not fufcep. tible of heat, is a very extraordinary affertion, since we are acquainted with no substance whatever that may not be heated Besides, a more intense cold may be artificially produced than what prevails in the lofty regions of the atmosphere. We must recur to other principles for the true solution of the fact. It is indiffe. rent what portion of the air first receives the heat; the effect depends entirely on the nature of its diftribution. If the atmosphere were of an uniform density throughout, the heat would, at all heights, be likewise the fame. But as the denfity varies according to the altitude, the distribution of heat is affected by that circumstance, and follows a certain corresponding law. I would gladly develope the principles from which this theory is deduced, but the popular nature of the prefent treatise forbids all abstract discussion. I shall therefore, content myself with gi wing a table of the diminution of heat at different altitudes. Diminion of heat, in degrees of Altitude in feet. 3,000 6,000 9,000 12,000 15,000 18,000 21,000 120 245 38 53 68 86 94호 1 The diminution of heat, on the ascent, is not quite so great in extensive continents; for the intercourse between the rare and the dense portions of the atmofphere is, in this cafe, neceffarily flow, and the heat, which is principally formed at the furface, will only be partially difperfed. It is a common mistake to suppose, that the fame heat obtains, at a certain depth, in every part of the globe. lobe. The fact is, that heat, originally derived from the sun, is communicated very flowly to the matter below the furface, which, therefore, does not feel the viciffitude of seasons, but retains the average temperature of the climate for many ages. Hence the utility of examining the heat of fprings which is the fame with that of the substances through which they flow. The |