holes to protect the guns from possible damage, but the damage could be easily inspected. The outer "skin" had burst open altogether, the pieces yawning with 5 or 6 feet apart. The two inner thicknesses of 1 inch each had also burst inward, though not breaking altogether, for it was only through the gash that thin pieces of timber protruded. One large nut of a screwbolt, which must have weighed many pounds, was broken right off, with about two dozen smaller ones, and hurled to the other side of the turret. The piece where it broke off being of course glittering, induced the first inspectors to consider it the top of the Paliser shell coming through, until the mistake was discovered. The wall was not pierced at all. The iron outer part was pierced, and the shell was still hot with the tremendous resistance it encountered. The teak had been

as

forced in, the bolts and rivets sent flying, but so much strength was left that it would have required a second shot exactly in the same place to entirely penetrate the turret. Captain Boys, of the gunnery ship "Excellent," who conducted the operations, in conjunction with Mr. Crossland, of the Council of Construction, and Mr. Eames, chief inspector of the machinery at Chatham, were of course highly pleased with the success, the turret working as smoothly by hand or steam ever. Captain Boys was in the captain's cabin of the "Glatton" at the time of firing, and assured us, that had he not known what was happening, he would have thought a tea-tray had dropped, while several of the men testified that the shock was nothing. This contrasts very favourably with the report of an American captain on board, who said that the turret to which he belonged came under fire, and the men were temporarily converted into "howling idiots"--a phase of insanity which seems by no means exclusively the property of turrets. To what the men may have been reduced if they had been compelled to remain in the turret it would be impossible to say, but a young goat which had been left there, and had placidly taken up its position at the foot of one gun, although looking somewhat

nervous about the eyes, was enabled to chew and apparently enjoy its cud. A rabbit and a fowl which had also been left did not protrude themselves on our notice; probably some of the men had been moved by compassion to usher them into a more peaceful life. They were not wounded, however, and that was all it was required to ascertain.

The second shot, fired at two, proved to be so successful that a third was found to be unnecessary. It struck the turret at the juncture with the deck, the weakest point. Indeed, from the upward direction of the penetrated holes, it would seem as if the missile had first struck the deck and turned off upwards. The spot selected was between the two ports, but the damage was even less. Inside nothing whatever could be seen of the effect, but on going lower down it was found that the base of the turret, or that part of the armour, rather, which ceases just below deck, was bulged downward. This was found to be equally the case with the first, and had they bulged a couple of inches more downward they must have jammed with the rain gutter which runs underneath it. This, however, could be cut out easily even during the action, and unless the friction was very severe, the steam-power could overcome that. On deck it was found that a few angleirons had been smashed, and a flange loosened; but no other damage was done. The dimensions of the hole were-depth 13·5, and breadth 11 inches; the resistance of the armour being so terrific as to force the steel head of the shell back again on to the deck. Great satisfaction was expressed by all those present, and a third shot was deemed unnecessary.-The Times.

CHARCOAL.

CHARCOAL is made by burning wood in such a manner that but little air shall be admitted during the operation, that is, only sufficient to keep up the combustion of the

more easily destroyed parts of the wood. The best result is produced, when the wood is quite excluded from the air, as in making acetic acid; but where large quantities of charcoal are used for common fuel, as in France, of course this process is too expensive. The usual way is to pile up billets of wood, and cover the whole with turf; when fired, the wood consumes gradually, and the charcoal is left behind. It is light and porous, and of a shining black colour; it weighs about one quarter as much as the wood used, and burns without flame or smoke, giving out a strong heat. When charcoal burns, it combines with part of the air, and is converted into a gas called carbonic acid, which, although invisible, is much heavier than air, and is a deadly poison; it is therefore necessary, when it is burning, always to have some opening at the bottom of the room. Many fatal accidents have arisen from people sleeping in a small room with a pot of burning charcoal, and no outlet for the poisonous vapour but the chimney, up which it will not pass on account of its weight. Charcoal enters into the composition of gunpowder, and is used for several other purposes. It is an excellent sweetener of foul water, and a few pieces should always be kept in the top of the filter when the water has any bad odour, or in the cistern, (where a filter is not used). A sort of cage, with a bottom of wire-netting, filled with charcoal, should always be fitted into the top of a cesspool, to suck in the poisonous gas that rises from it. When powdered, it has also the power of taking away the colour of many liquids, as well as the bad smell; vinegar, if warmed with powdered charcoal and then strained, will be almost colourless. Water-butts are sometimes burnt or charred inside, that the water may be better preserved in them.

Chemically considered, charcoal consists of carbon, with a certain amount of earthy matter, the ashes or earthy part of the wood from which it was made, but these ashes may be easily removed by maceration in an acid, the charcoal then remains unaltered in appearance, and consists of carbon, but its structure is exceedingly porous.

ILLUSTRATIONS OF LIGHT.

SIR CHARLES BELL has described some curious phenomena in optics, which will be very easily comprehended by the previous knowledge of two or three acknowledged facts.

Vision, or sight, is produced by the rays of light, (which fall from the sun or any other source of light, on an object,) being reflected from thence, so as to fall on the retina or back part of the eye; thus the moon is seen by the rays of light (which fall on it from the sun), being reflected back to the eye, and a tree, a house, or any other object is seen by the daylight (which falls on the tree or the house), being in like manner reflected on the eye.

A ray of light is compounded of many rays, and may be divided into seven, capable of causing to the eye the sensation of so many different colours; red, orange, yellow, green, blue, indigo, and violet. If all these are reflected together, they produce on the retina the sensation of white, as from this paper. If these colours, in their proper order and proportion, be painted on the broad rim of a wheel, and that wheel be swiftly turned round, it will appear of an uniform and white colour. Black is the absence of all colour, when the rays are all absorbed and none reflected. The separation of a ray of light into colours is a beautiful experiment, and easily performed. Get a prism, which may be procured at any optician's for a trifle; it is a piece of glass a few inches in length, with three sides in the form of a triangle.

Place this prism, P, opposite to a hole in the closed window shutter or screen, so that a beam of light, S, from the sun may pass through, and be received on an opposite screen, E. The image of the sun will appear on the paper of an oblong form, rounded at the extremities, and straight at the edges; this image is called the prismatic spectrum, the principal part of which will be composed of seven parallel spaces

of different breadths, and exhibiting seven different colours. The lowest colour is red, and above it appears successively, orange, yellow, green, blue, indigo, and violet, which is the highest coloured space. If we

Fig. 1.

suppose the coloured part of the spectrum to be divided into one hundred parts, the red space is found to occupy eleven of those parts, the orange eight, the yellow fourteen, the green seventeen, the blue seventeen, the indigo eleven, and the violet twenty-two.

The retina is the internal coat of the eye; it consists of a delicate pulpy nervous matter, which is contained between two membranes of extreme fineness, and these membranes both support it and give to its surfaces a smoothness mathematically correct. The matter of the nerves, as well as their supporting membranes, are perfectly transparent during life. Vision is not excited by light, unless the rays penetrate through the trans parent retina and reach the exterior surface from within. The retina is subject to exhaustion. When a coloured ray of light impinges continuously on the same part of the retina, the retina becomes less sensible to it, but more sensible to a ray of the opposite colour. When the eye is fixed upon a point, the lights, shades, and colours of objects continuing to strike upon the