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water, and is then plunged into the salt and water and carefully moved round with a copper hoop; when the yellow colour has departed, the plate is placed on a desk at an angle of forty-five, and distilled water warm, but not boiling, is carefully poured over the surface. As soon as the moisture has evaporated, the operation is completed, and the drawing may be safely exposed to the full light of day. The appearance of these drawings is very peculiar. The shadows are a dull grey, varying until they become almost black, and though the pictures they delineate are accurate in the extreme, they are not pleasing. They appear unnatural and look somewhat like a moonlight scene. The Daguerreotype, with all its necessary apparatus, is manufactured and sold in Paris, for about £20. In Bombay, where the sun is always powerful, pictures of scenery could daily be produced. And one great advantage is, that for copying, their fidelity to nature will strongly recommend them. We cannot take leave of the Adelaide Gallery without expressing our admiration of the usefulness of such an institution. There is a powerful microscope and lectures upon several subjects are delivered, and for all this, the admission is only one shilling.

POLYTECHNIC INSTITUTION.-We often went to see this Institution, 309, Regent Street, it was established in 1838, upon the same principle as the Gallery of Practical Science, in the

Lowther Arcade, but having had the advantage of seeing the working of that institution, it started with peculiar advantages over its predecessor, and we are quite sure that there is not in any country to be procured so much intellectual amusement for a shilling, as is to be had at the Polytechnic Institution; for you can be constantly amused and your mind improved, from half-past ten in the morning until half-past four, and only pay one shilling, or you can go from seven until nearly eleven at night, for a similar sum. A band of music plays daily from three to five o'clock, and in the evening from about eight until the exhibition closes. There are thirty different rooms connected with the institution. The whole building is three hundred and twenty feet in length.

The first apartment you enter, is a hall fortyfive feet long and forty feet wide, devoted to machinery and manufactures. All the machines in this hall are worked by steam power. There is a lathe for turning ivory, hard woods, brass, &c., with all the apparatus, for the most beautiful of ornamental turning. A loom for weaving ribbons, a loom for weaving checks, a braiding machine, a twisting machine, a warping mill, and a beautiful four horse power steam engine. On the opposite side is a gem engraver at work, a copper plate printing press at work, steel and copper plates engraving, also a manufactory for optical instruments,

and for grinding and preparing lenses for telescopes and glasses for spectacles, &c.

You then proceed to the great hall, one hundred and twenty-feet long, forty feet wide, and forty feet high; in the centre are two canals with a surface of seven hundred feet of water, attached to which are all the appurtenances of a dock yard, constructed by the government engineers, the models deposited by permission of the lords of the admiralty, with a great many locks to keep up a head of water upon canals, and a series of water wheels in motion, to illustrate lectures on naval architecture and hydrostatics. At the end of the canal is a deep reservoir of water into which a diving bell capable of containing four or five persons is lowered to a considerable depth under water, air being supplied by two powerful air pumps, so that visitors may descend with convenience, and whilst we were there we saw several persons go down, among whom were some ladies, the only inconvenience experienced whilst under the water is a great pressure upon the inside of the ears, which to stout persons of a full habit of body becomes very painfully troublesome. We know several persons who have descended and they have felt no ill effects from it. A diver, clothed in a patent water and air tight diving dress, goes down a ladder to the bottom of the reservoir of water, being supplied from the air pump with air through a tube that enters into his

dress; he is when prepared to descend, the oddest looking creature ever seen, he has an immense helmet of white metal over his head, and in front of his eyes are two large thick pieces of glass protected by bars of metal, this helmet is strongly strapped to his water proof dress, and he then presents a most laughable appearance; he is obliged to load himself with heavy weights before he gets into the water, otherwise his buoyancy would cause him to float on the surface, but thus loaded down he goes, and will pick up money or any small thing thrown down to him, walking about the bottom of the clear water as unconcerned as possible; a model of a ship containing a small charge of gunpowder is sunk some depth under the water, to which the diver attaches wires, communicating at a considerable distance with a Voltaic battery which when connected instantly explodes the powder and the vessel is shattered to pieces, thus illustrating Colonel Pasley's clever method of destroying the wreck of the Royal George at Spithead.

An illustration of the patented plan for preventing ships from sinking and for raising them when sunk without injury is also exhibited. The diving bell is made of cast iron, open at the bottom with seats all around, and is of the weight of three tons; the interior for the divers is lighted by openings in the crown of thick plate glass, which are firmly secured by brass frames screwed to the

bell: it is suspended by a massive chain to a large swing crane, with a powerful crab, the windlass of which grooved spirally and the chain passes four times over it into the well beneath, to which chain is suspended the compensation weights, and it is so accurately arranged, that the weight of the bell is at all depths counterpoised by the weight acting upon the spiral shaft; the bell is put into action several times a day, and visitors may safely descend a considerable depth into the tank, which with canals, holds nearly a thousand gallons of water, the whole of which if required, can be emptied in less than one minute. The diver's dress, helmet, air-tubes, &c., are patented articles, having been introduced by Mr. Deane. With the diving bell and the diver's dress, every thing almost can now be performed under water; the tops of piles can be sawn off, an eye bolt can be driven into a sunken vessel to make purchases fast to, in order that she may be hove up. Rocks can be blasted by the introduction into them, at any depth under water, of charges of powder, which can be exploded through water proof tubes, or by a galvanic battery by wires.

A gallery runs all round this hall, which is thickly studded with models and curiosities of all kinds. At each end of the gallery is placed large metallic circular reflectors, about twelve feet in diameter; they must be quite one hundred feet apart from each other, and yet, although there is

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