And yet I grieve not-for the time For memory to dwell upon. O'er many a field and woodland far, In scenes where want and sorrow are. The past, a hallow'd track of beauty, And when I think, I'll think of bliss, Let Fancy rest, on that which is Like Hope upon her anchor leaning. A plant whose bloom to earth is given, CHEMICAL ESSAYS.-ESSAY IV. (Continued from col. 516.) In my brief essay on Oxygen, I observed that the blood is converted into a red oxyde, by the oxygen of the atmosphere acting upon the iron contained in the blood; but I should have mentioned also, that there are many modern chemists who deny the existence of iron in the globules of the blood; notwithstanding which, I am still of opinion that the globules of the blood do contain a small quantity of iron; the traces of which I have always found sufficiently distinct to satisfy myself as to the reality of its existence. The oxygen of the atmosphere cannot enter into chemical combination with the carbon thrown off by the blood, to constitute Carbonic Acid Gas, without a portion of caloric being evolved; now this caloric is seized by the arterial blood, and when it passes on to the veins, its capacity for caloric is diminished as much as it had been increased in the lungs; the caloric, therefore, is gradually evolved in the course of the circulation through the minute vessels over the whole body, giving stimulus to the operations of the animal economy, and a beautiful provision for the maintenance of a uniform animal temperature. The blood, then, in passing through the lungs, is freed of two noxious principles, namely, carbon and hydrogen; and indeed the extreme great quantity of the former of these is astonishing, amounting to no less than 11 ounces in the 24 hours. A small quantity of oxygen is absorbed ; and the arterial blood becomes loaded with caloric. The support which atmospheric air administers to combustion, entirely depends upon the presence of Oxygen Gas; for combustion will never take place without this gas be present. The atmospheric air is decomposed; the combustible body absorbs its oxygen; while its other constituent parts are set at liberty. Air is invisible, colourless, and elastic, capable of indefinite expansion and compression. Elasticity is one of the most obvious properties of air, and it is, perhaps, the one upon which philosophers have made the greatest number of experiments. We are acquainted with a great number of facts, illustrative of the air contracting its volume, and recovering the state from whence it was displaced, upon the entire removal of the causes by which it was compressed. If a bladder, containing a small quantity of air, be tied up with a string fast round its neck, and placed under the receiver of an air pump, it will gradually swell as the receiver is exhausted, till it becomes quite full, which is owing to the elasticity of the small quantity of air contained in the bladder, dilating and expanding itself on the removal of the atmospheric pressure. The same expansion takes place if we carry the bladder to the top of a very high mountain. So likewise bubbles of air rising from the bottom of a glass of water, gradually dilate as they approach towards its surface, owing to the gradual diminution of the pressure of the water. It is also owing to the elasticity of the air, that thin glass globes filled with air burst asunder upon the exhaustion of the receiver of an air pump. The generality of fishes are furnished with an air bladder; which is placed very near to the backbone; and this they have the power of contracting and dilating at pleasure. By contracting this bladder, and thereby condensing the air within it, they can, with very little exertion, render themselves specifically heavier than water, and enable themselves to sink to the bottom. On dissection of the bladder of fishes, we find that it has an extremely strong muscular coat, by means of which the animal has the power of contracting and dilating its bladder to a smaller or greater size as best suits its convenience; and thereby of swimming in any depth of water, or rising to the surface with the greatest facility. It is upon this property of the air of which we have been speaking, and upon which we shall make some further observations, that the forcing pump and air-gun are constructed; and it is also by this property that air is chiefly distinguished from other fluids. It is the generally received opinion, that the atmospheric air owes its elasticity entirely to the caloric it contains. As a proof of the great elasticity of the air, it will be sufficient to observe, that Mr. Boyle succeeded in dilating it, till it occupied nearly 14,000 times its ordinary space, without the application of heat, and by only removing the pressure by means of an air-pump. The elasticity of the air is diminished by cold, and greatly increased by the application of heat, as may be shewn by holding a bladder, containing a very small quantity of air, to the fire; upon the rarefaction of the inclosed air, it will gradually expand till it appears quite plump, and will return to its former flaccid state, when reduced to its former temperature. It is upon this principle that the structure and use of the thermometer depends. The next property of the air which I shall notice, is its fluidity; a property which it never loses; whether under the strongest pressure, or exposed to the greatest artificial cold we are able to produce. In all bodies in which it lodges, or is kept in closestopped vessels for a great number of years, it still remains in a state of permanent fluidity. The next obvious property of the air is, its weight or gravity:-a property which was discovered by the immortal Galileo, a celebrated astronomer and mathematician, born in the year 1564. Although Galileo was well acquainted with the weight or gravity of air as a body, yet it is to his ingenious pupil, Torricelli, that we are indebted for the discovery, that it is the weight and pressure of the atmosphere which keeps water raised in pumps, and mercury raised in barometrical tubes, and that a column of air, of the whole height of our atmosphere, is equal to a column of water of equal base, 34 or 35 feet high, and a column of mercury of an equal base, 30 inches high; hence water never ascends in common pumps higher than 35 feet, or mercury in barometrical tubes higher than 31 inches. If the student (for the use of whom these essays have been principally written) is in possession of an airpump, he will derive considerable advantage from the performance of the following experiment. Take a common glass cylinder, or receiver, open at both ends, and place it upon the plate of the air pump. The experimentalist is now to cover the uppermost open end of the cylinder with the palm of his hand, and exhaust the cylinder of its air. The pressure being now entirely taken off from under the hand, he will immediately become sensible of an almost insupportable weight, which presses down the hand to the receiver, with a force sufficient to cause considerable pain, and indeed to break the hand, if it is not soon removed from its uneasy situation, which can only be done by the re-admission of air into the receiver. Air can be even weighed with as much accuracy as any other substance. The difference of weight between a vessel filled with air, and another vessel exhausted of its air, may be readily ascertained, and this difference will be proportionally more sensible, if the vessel be filled with condensed air. A quart measure of atmospheric air taken near the surface of the earth, weighs about 17 grains. The specific gravity of atmospheric air, as determined by Sir George Shuckburgh, is 0.0012, the barometer being at 30 inches, and the thermometer between 50 and 60 deg. It is, therefore, 816 times lighter than water. I have said that the whole pressure of the atmosphere is equal to a column of mercury of an equal base, and 30 inches high, and as a column of mer tion, as shewn by the following Table. Height in Miles above the surface of the earth. 7 Number of times rarer. 4 14 16 21 64 28 256 35 1024 42 4096 49 16384 56 65536 cury of this height, and an inch square, is found to weigh 15 pounds, it follows that the pressure of the atmosphere amounts to 15 pounds on every square inch of the earth's surface; consequently, the pressure on every square foot of surface, amounts to 2160 pounds. If we reckon the external surface of a man's body to be about 15 square feet, and the ordinary weight of the atmosphere 2160 pounds on every square foot, he will sustain a weight amounting to nearly 14 tons. The weight of the atmosphere, however, is not always the same, and indeed the difference in its weight from the natural changes in the state of the air is often very considerable, and it would be no difficult task to shew that the difference in the weight of the atmosphere on the surface of a man's body, supposing it, as before, to be equal to 15 square feet, is nearly 1 ton. We have, therefore, no reason to wonder that invalids do so powerfully experience the periments relative to the aqueous vavariation of the additional pressure of pour contained in the atmosphere, I refer the reader to the writings of the atmosphere; but we have reason to wonder that so great an additional that excellent chemist, Mr. Dalton, of pressure should be borne at all without Manchester. I am well aware of the truth of the ancient maxim, “A great crushing the frame of our bodies to book is a great evil," and I have enpieces. But the fact is simply this, the interior cavities of our bodies deavoured to improve upon this maxalways contain some elastic fluids, the im, of the importance of which as a re-action of which is sufficient to ba-modern writer, I am so well satisfied; lance the weight of the external atmosphere. Dr. Vince has given the pressure or weight of this ambient fluid on the whole surface of the earth at 77,670,297,973,563,429 tons. Dr. meter. an Cotes reckons the weight equivalent to a globe of lead 60 miles in diaAnd Dr. Thompson gives 11,911,163,227,258,181,818 pounds, avoirdupois, for the whole weight of the atmosphere. As air is elastic fluid, and its density being always proportional to the weight by which it is compressed, it follows that its density diminishes according to its distance from the surface of the earth; consequently, the air on the top of very high buildings is considerably rarer than that at the surface of the earth, whichis compressed by the whole weight of the incumbent atmosphere. Philosophers have demonstrated, that if the altitudes in the air do continually increase in arithmetical proportion, the rarity of the air will be in continued geometrical propor 140 274877906944 1099511627776 For some of the most accurate ex but I have already extended this paper to a greater length than I had I am obliged to suppress the latter originally intended, for which reason part of it, containing observations on the existence of those bodies, which, although they cannot be considered as constituent parts of the atmosphere, have been occasionally found in it. I shall therefore conclude with noticing the following principal errors of the press, in my preceding essays, which the candid and liberal reader will please to correct with a pen, the one marked with an asterisk materially affects the sense. Col. *26, line 45, for atmospheric air, read water. Col. 28, line 43, for oxymuriate, read oxymuriatic. Col. 227, line 52, for sulphurat, read sulphuret. Col. 228, lines 45 and 47, for Kerwan, read Kirwan. Col. 228, line 49, for of, read by. Col. 347, line 39, for were, read are. Col. 347, line 55, for was, read is. Handsworth Woodhouse, near Sheffield, JOHN NUTTALL. 15th April, 1822. DIALOGUE BETWEEN MAHOMET & THE DUKE OF GUISE, IN THE SHADES. Mah.-Come, let us sit down here, and laugh a little together at all those tricks you and I have put upon the world. Duke. With all my heart: What better use could we have made of it? Is mankind fit for any thing but to be cozened? Mah. Yet you must confess that my way is the more noble, and had something of the sublime in it: you did your business by nothing but mere cringing. Duke. You are mistaken: there goes more to popularity than that comes to; and yet the cringing you speak of, when 'tis of the mind, is no such easy matter. Mah. Not to so lofty a one as yours; perhaps low stooping makes a tall man's back ache. Duke. You are merry, Sir; therefore I suppose you will not be loth to confess some of your noble tricks, as you call them. Mah.-On condition you tell yours. Duke.-Agreed, and pray begin: Mine was but lay-dissembling, which ought to give place to divine hypocrisy. Mah. You have heard of my pigeon, I warrant. Duke.-Yes, and of your owls too: Could such a gross thing pass among them? Mah. As easily as a creed: nay, at last I might have spared my pains of teaching the pretty bird; for the rabble would have fancied her at my ear, though she had been all the while fluttering in their faces. Duke.-Nay, though she had been picking out their eyes, for I must acknowledge you the best of all the bigot-makers that ever I read of. My superstitious coxcombs never reached either the devotion, or morality, of yours. Mah. That is, because I laid a better bait than any in your legends. Is not that more desirable, than passing through flames of purgatory, to only spiritual imaginary pleasures? is also unconceivable. But this was not your fault, the schoolmen should have mended it. Duke.-Abundance of them have tried to do it. Mah. But to no purpose; 'tis such a patched business, between the superstitions of old Rome and new Rome, blended together, that the wise at last were ashamed to wear it, and did as good as throw it quite off, by what they called a Reformation. Duke.-Very well, Sir; but is any thing so ridiculous as your lies? Mah. Yes, your legends. But shall I confess a truth which will make amends for all my lies? Duke. That will be something difficult. Mah. Why; I began to believe them myself, at last. Duke.-Oh, ridiculous! Mah.-I was so very fortunate, that I fancied myself a kind of favourite of heaven; and if I had been put to it, 'tis not impossible but I might have died a martyr for a religion of my own invention. Duke. That is more incredible than any thing in your whole Alcoran. Mah. Then, for all your popularity, you are not much skilled in mankind. Why, we are all of us but overgrown children, afraid in the dark of our own scarecrows; and as fond too sometimes of the babies we ourselves trick up. Duke.-Is it possible? Mah. Yes, to flatter a man into any thing. Alexander himself, the pupil of Aristotle, and the very top of all humanity, did at last believe that Jupiter was his father; and by his saying that sleep had best convinced him of his being mortal, 'tis plain he sometimes doubted it. Duke.-Like enough. And did your instruments, Sergius the monk, and the rest of them, believe themselves too? Mah.-Religious sort of men, you know, outdo all others in flattery; and I having set them up for my ends, they sanctified me for theirs, till we almost acted ourselves into a real veneration for one another. But tell me now a little of your pranks, for you played them I hear to some purpose. Duke.-I had so, if the business at Blois had not prevented me. 2 Mah. But you had a fine time of it | worth a thousand of your school-distill then. tinctions, which are but slight cobwebs spun out of case and idleness. Being witty out of season, is one sort of folly. A HUMOURIST. Duke. Very far from it. Rowing in the galleys is nothing to the toil of popularity: but ambition is rebutted with nothing. Mah.-Why, pray where was all this trouble? Duke.-First, I never said one word I thought, and passed my life in gaining surly people's affections, whom all the while I contemned for being deceived so grossly. Mah. But yet you had the pleasure of advancing your friends every day. Duke. As seldom as possible, and I did it always unwillingly. Mah.-How then came they to follow you so much, and almost adore you as you went along the streets? Duke.-Now 'tis you are catched; I am glad to find you so much out at the knowledge of mankind. Mah.-Why pray, what is the mat ter? Duke.-Obliging men is not the way to win them. Mah. Methinks it should be so. Duke.-Quite contrary: every man I advanced, thinking his business done, never minded me afterwards; so there I lost a friend, and made a hundred enemies out of envy to him. Mah.--But yet you ordered your business so as to have a great many friends, and few enemies, except the Huguenots. THE PEDIGREE AND RESIDENCE OF HAPPINESS.-A VISION. "The visions of my head troubled me." So said Daniel, a long time past: I may truly repeat his declaration, and shall think it a favourable circumstance if they do not trouble the reader also. In my dream, I found myself upon a lofty hill, whose summit was enveloped in clouds, and every thing upon it had a most extravagant appearance. Every person seemed most fantastically dressed and whimsically employed; some were bottling up the air in phials, to discover what it was made of; some were making scales to weigh the planets in; some finding out a new method of guiding the tides; and some a new way for forging thunder-bolts; some were busy in mending the Bible by their reason, and some were accommodating religion to their passions and failings; some decked themselves in cobwebs; some strutted along in ribbons; some making themselves wings of wax ; and some building pyramids of snow. "Bless me," said I, rubbing my Duke.-True, but it was only by eyes, "where am I got to?" A deseeming kind to every body, and all cent-looking man, who had the apthe while caring for nobody. I used pearance of an honest preacher, and them just like a herd of beasts, as happened to be near me, replied, indeed they are; increased their num-"This, Sir, is the Hill of Conceit; ber all the ways I could, valued them according to their use, but loved none. Would you have had me fond of a black ox or a red cow? Mah. For aught I see, never man was beloved so much, or deserved it so little. Duke. Thank you for your compliment; and not to be ungrateful, I believe never any religion has been spread or practised so much as yours, and yet without the least shadow of wit or learning. Mah. That is the reason it took so much. Whoever aims at mankind must not shoot high: fine nets may catch birds, but they never hold beasts. Mine were coarse and strong, and these are the self-made philosophers and doctors of the place; take care you are not infected with their madness; make haste to yonder valley, or you will soon catch the pestilence of the place." Thanking him for his advice, and inquiring his name, I turned my steps downward. "I am Plain Truth," said he; "mind how you proceed." This caution was necessary, for I was soon surrounded by a host of projectors, and proposers, and authors, and such like persons, who solicited my subscription and patronage to their different schemes and proposals; but I forced myself from them and made my escape, at the expense of a few shillings, over |