promontory being extended by the ashes about 800 feet further out, gives additional reason to credit the statement.

On the 3rd of March, nearly two months after this great eruption, the volcano remained in a state of activity, but not ejecting ashes. By some geologists it has been considered that heavy eruptions of fine scoriaceous matter tend, by their falling again into the crater, to restore the volcano to a quiescent state, and that therefore this phenomenon more usually attends the conclusion of an explosion. In this particular instance it appears that the first effect of the explosion was to blow out of the crater, and finally triturate, the scoria and ashes left there twentysix years before.

In the districts of Segovia, Comagagua, Choluteca, Nacaome, and Tegusigalpa, immense deluges of rain followed these clouds of ashes, and again gave rise to a fetid, disagreeable odour. At this season such an occurrence was extraordinary, and almost unprecedented in Central America.

I shall conclude by stating that the ashes reached as far as Chiapa to the north, upwards of 400 leagues to windward of the volcano: thus proving the existence of a counter-current of wind in the higher regions of the atmosphere. At St. Anne's, Jamaica, on the 24th and 25th of January, the sun was obscured, and not only there, but over the whole island, showers of fine ashes were observed to fall. The distance in a direct line north-easterly is about 700 miles; consequently the ashes must have travelled at the rate of about 170 miles per diem.

Captain Eden, of His Majesty's ship Conway, informs me, that in lat. 7° 26' north, and long. 104° 45′ west, when 900 miles from the nearest land, and 1100 from the volcano, he ran forty miles through floating pumice, some of which was in pieces of considerable size.

The latitude of Cosegüina is 13° north, and longitude 87° 3' west. Its height above the sea is computed at 500 feet.

No volcanic eruption in modern times has been recorded that reached the frightful extent of the one of which I have now had the honour of laying an account before the Royal Society. The explosion of Tomboro, in Sumbaya, in 1815, described in the Memoirs of the late lamented Sir Thomas Stamford Raffles, more nearly approaches it than any other with which I am acquainted.

[From the Philosophical Transactions, for 1386.]

HAVING fully discussed the nature and properties of

oxygen, and many of the manipulations in pneumatic chemistry; the way is in a great measure prepared, for the consideration of other gases, and amongst them the next that I shall mention is chlorine. It is a very singular elementary body, as will presently appear; and although I call it a gas, in accordance with the common parlance of the laboratory, yet, strictly speaking, it does not merit that title, and should rather be styled a vapour.

Now oxygen, as far as our present knowledge goes, is a gas; cool it to the lowest possible degree by the most powerful frigorific processes, or submit it to the most intense mechanical pressure known, it undergoes no change save that of bulk; it does not become either solid or fluid, but remains permanently gaseous at all temperatures and pressures. Not so does chlorine, under similar treatment; for, if a little aqueous vapour be present in it, when cooled down to 32° of Fahrenheit's scale, it becomes a white crystalline solid, or if perfectly dry, and submitted to pressure, it becomes a bright yellow liquid; it is, therefore, far from being permanently gaseous, and is, in fact, a true vapour.

The temperature of this climate is rarely so low as to alter the vaporous form of chlorine, and, therefore, it may be operated upon in a way somewhat analogous to that already described for oxygen.

Having premised thus much regarding the nature of chlorine, I have now to point out to you the method of extricating it from its combinations, the means of collecting it, and, lastly, some of its most remarkable properties.

The pneumatic trough must be filled to its proper level with hot water, at such a temperature that the hand can just be borne in it without inconvenience, and the bottles, or jars, destined to receive the chlorine, must likewise be filled with similar hot water. The glass stoppers must be greased, as already directed. A tubulated glass retort, holding about a wine-pint, and having a long neck, is now to be about half filled with black oxide of manganese; arrange it so that the beak or end of the neck just dips beneath the water at the hole in the shelf of the pneumatic trough; this is easily done if the retort is placed upon that very useful contrivance, called a retort-stand, the sliding-rings of which admit of ready adjustment, to a great many lengths and heights.

The proper adjustment having been made, and everything so arranged that the retort can be removed, and replaced without loss of time; remove it, and place a small glass or earthen funnel in the tubulure, and then quickly, but carefully, pour in as much strong muriatic acid as will moisten the manganese into a thin paste. Do not pour in the acid all at once, but a little at a time, and shake the retort round and round, so that all the manganese may be duly moistened; if you pour all the acid on suddenly, the chances are that it will be absorbed by the upper parts of the manganese, whilst the lower remain perfectly dry, and this would

almost invariably cause the fracture of the retort, if heat was applied, and perhaps, before the operation of generating chlorine is finished, it will be necessary to apply a little heat: but of this presently.

Let us suppose the acid now properly mixed with the manganese, withdraw the funnel quickly, insert the stopper of the tubulure, place the retort on the retort-stand, a bottle over the hole on the shelf of the trough, and thus far we are successful. Let us proceed further.

Bubbles of some aëriform or gaseous matter, are now rising through the water into the bottle-a sort of fermentation or effervescence is taking place between the materials in the retort; and now its arch and neck appear of a bright yellow colour, this same tint is communicated to the bubbles rising in the bottle. Chlorine is now evolving, and it is a yellow

gas.

The first bubbles that came over were not yellow, because they were not bubbles of chlorine, but only those of common air, that the retort contained; the chlorine generating behind, forced this forward.

When you judge that as much aëriform matter has passed into the bottle, as is equal to the capacity of the retort, the bottle must be slid gently on one side, and its place supplied by another, and now you see the yellow colour of pure chlorine. Remember always to make your transfer of bottles quickly, steadily, and cautiously, and to suffer as few bubbles as possible to escape into the room, for chlorine is a highly noxious and suffocating body, eminently hurtful to the lungs, even when very largely mixed with air: it is much the best to perform the operation in the open air, or under a shed, so that if any accidental escape of the gas takes place, the wind may waft it away before it affects the lungs. Perhaps, in spite of all your precautions, a puff of the gas may escape, and annoy you, producing coughing, and a most disagreeable, yet indescribable, sensation in the throat, which is particularly distressing; to alleviate this, I recommend a lump of sugar soaked in weak spirits of wine, with a few drops of sal volatile, to be held in the mouth until it dissolves.

You have now to dispose of the impure air and chlorine in the first bottle: stop it under water, take it to some distance from where you are at work, and then removing the stopper, let its contents escape: attend now to the second bottle, which is rapidly filling with pure chlorine; when full, and no water remaining in it, stopper and remove it, place on another, always full of hot water, remember, and if that in the trough cools, more hot water must be added, so as to keep up the temperature at which you set out.

The reason why hot water is necessary in this process is, because chlorine is absorbed or dissolved by cold water, and if you used it, you would scarcely get a solitary bubble to rise, at all events not to remain in the bottle, but the water would become a strong solution of chlorine: this I shall speak of presently.

Now although, perhaps, chlorine has hitherto been evolving quietly, yet it very often happens that the materials in the retort foam up, and boil over,―or effervesce over is perhaps a more correct expression,-the neck of the retort becomes filled with a black foamy mass of the mixture, it runs into the trough, and soils all the water. This is very annoying, VOL. II.

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but there is no help for it; if it once happens, you had better stop work and begin again, the expense is barely worth mention a single farthing! The larger the retort, the less likely is this to happen, because the materials have ample room to swell and foam in its body, without rising into the neck. A little practice will soon enable you to apportion all matters rightly.

Supposing the accident does not take place, the evolution of chlorine becomes sluggish after a time, and then you may excite it by the gentle heat of a spirit-lamp; but if, after continuing this heat for some time, you find a bubble or two, very suddenly evolved, with a sort of jerk, and a little water at the same instant rising in the neck of the retort, you may be sure that no more chlorine is coming over, but that the heat has converted part of the water of the muriatic acid into steam, which, meeting with the water in the trough, at a lower temperature than 212°, is suddenly condensed, and produces the jerk, or concussion; you must, therefore, stop the process, by taking away the lamp, and taking out the stopper from the tubulure.

If you left the stopper in, see what would happen,-why, as the retort cooled, the water from the trough would rush in and fill it, perhaps break it. This cannot happen if the stopper is out, or lightly inserted with a bit of paper or thread between the ground surfaces to admit air.

When you judge that it can be effected without risk, empty the retort, wash it well out, and set it to drain, so that it may be ready for a similar operation on a future occasion. Whenever you finish any experimenting, cleanse your vessels and apparatus, and set them by in their proper places, as soon as possible; then they will always be ready to your hands, and at the year's end, you will have saved a large proportion of valuable time, which would otherwise have been lost in hunting after things out of place, amidst a miscellaneous collection of dirty bottles, glasses, retorts, and chemicals.

Always observe the two following "golden rules."

I.

66 Never put off until to-morrow, that which can be done to-day." II. "A place for everything, and everything in place."

In your laboratory you will find shelves far more useful and convenient than drawers. You have all things immediately under observation and command on shelves, whereas you are often tempted to cram dirty things away in drawers; so that the laboratory may appear neat to the casual observer. Had I my will, I would have no drawers in the laboratory.

Now let us proceed to the examination of the nature and properties of chlorine.

The most obvious property is its greenish yellow colour, and hence the derivation of the term chlorine. I have already said that it is injurious to life, but it supports combustion to some extent; I mean common combustion, as of a candle or taper, and of this you can easily convince yourself, by putting a lighted taper into a small bottle of it; the brilliancy of the flame is greatly diminished, it is red and smoky, very different to what happened with oxygen. But although the combustion of a taper is so imperfectly and languidly supported by chlorine, yet other substances

will burn in it with energy; and substances, too, that are not usually considered combustible.

For example, take the metal antimony, reduce some of it to a very fine powder in a Wedgwood mortar; place some of this on a bit of bent card, then loosen the stopper of a bottle of chlorine, and throw in the antimony, it takes fire spontaneously, and burns with much splendour, producing a large quantity of white fumes. This result will not take place in oxygen, and you would not have anticipated it in chlorine, after seeing how sluggishly the flaming hot taper burned: how curious then is it to see the cold metal spontaneously burst into flame! this is an instance of intense chemical affinity.

Now observe how slight a thing will modify or prevent this affinity between chlorine and antimony. Drop a lump of the metal into the gas, there is no spontaneous combustion, no intense or immediate action: in the course of time, the antimony will become incrusted with a white powder, and no chlorine will be found in the bottle.

How is all this? why it is an instance of mechanical aggregation opposing chemical affinity; the metal is one hard compact mass, strongly aggregated, and, therefore, the chlorine has this to contend with and overcome before chemical action can ensue; it takes place slowly in this instance, but in the other, where the metal was in fine powder, aggregation was, to a certain extent, mechanically overcome, the chlorine had little to contend with, but instantaneously exerted its action on each minute particle, intensely and rapidly, the usual attendants upon which intense chemical affinity are the evolution of light and heat.

Let us take another metal: we will select copper, in that form well known as “Dutch gold,” that is in fine leaves; now slightly breathe on one end of a glass rod, about ten inches long, and cause one or two leaves of "Dutch gold” to adhere to the damp surface; then open a bottle of chlorine, and quickly plunge in the metal leaves, they instantly take fire spontaneously, and burn with a fine red light. A greenish-yellow solid substance results from this experiment.

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A small lump of copper, or Dutch gold," will not burn in this manner, but is only slowly acted upon as just now stated regarding antimony.

A bit of phosphorus, placed in a deflagrating spoon, will take fire spontaneously in chlorine, and burn with a pale flame, producing white fumes: you remember how splendidly it burned in oxygen; the combustion in this instance is far inferior in splendour, nevertheless the affinity is intense.

Now let us examine the nature of the products of these three cases of spontaneous combustion: I have already stated that when a metal is burned in oxygen, the product is styled an oxide; and when a similar phenomenon takes place in chlorine, the product is styled a chloride; thus the first result was a chloride of antimony, the second a chloride of copper, and the third a chloride of phosphorus; these are all very important combinations, but I do not enter upon their natures in detail, because it would be out of place here, where I am only showing the general characters of chlorine.

Cold water readily dissolves chlorine. Open a bottle of the gas, and