Page:All the Year Round - Series 2 - Volume 1.djvu/628

 he (or was it his grandfather?) used to turn out the birds with feathery tails, and has a front place on the floor. We liked him better where he was; it was a quieter place, a good place to retire to when it was considered advisable to avoid temporarily the observation of our elders. The wheel of life—it was called something else when we knew it first, years back, and before it was brought out as a great novelty a few months ago—still spins round in the gallery; there is a sample vase of wax fruit that seems like an old familiar friend. One side of the gallery is ornamented with sectional views of geological strata, surmounted in each case by an appropriate landscape. The boys have a bad time of it in this gallery; as we pass by, fragments of geological information, more or less (generally more) inaccurate, are borne upon the air; blue lias, London clay, and old red sandstone are on active service.

The glass cases along the other gallery are filled with a most heterogeneous mixture of goods. Why Miss Blank should have presented the Institution with her false teeth, not to say gums, it is difficult to make out; and although a wood bracket, "carved, by permission, by a footman in service during his leisure moments when the family are dining out" (he seems to have had no leisure moments but under these circumstances), is highly creditable to its author, it can scarcely be considered either remarkable or diverting. Turning from objects such as these, there is on view a collection of busts of a very appalling nature: one, in a wig, presumably that of the late Lord Brougham, being unspeakably tremendous; but candour compels the admission that outside the lecture-rooms, at all events, there is not much more amusement than in the old days, perhaps even not quite so much. The bazaar element is decidedly stronger than of yore, and it may be delicately hinted that the ladies who preside at the stalls are somewhat pertinacious in their efforts to do business. And it cannot with truth be said that the objects for sale possess any particular attraction, being, indeed, for the most part, of a rather uninteresting and unsatisfactory sort.

But our business is not with patent cement, or novel processes in photography, or feeble little "specimens." We have a more important matter on hand.

Our classical reminiscences have left us with the conviction that, when Vulcan forged the bolts of Jove, the scene must have been, as the graphic reporter has it, "one of terrific grandeur." We pictured to ourselves the lame god and his Cyclopean assistants, hammering and forging the celestial weapons in some flaming cavern of Etna or Vesuvius, amid an eternal din like that of a chain-cable factory crossed with a rolling-mill. Lurid smoke rolls heavily upward through the fiery air; the molten lava rushes forth on its work of destruction; while the lightnings, that now and again play round the top of the groaning mountain, proclaim to a trembling world the tremendous nature of the operations going on below.

Although we had inspected electrical machines, and had looked as scientific as possible at the sparks we had seen elicited from them, the grand and heroic idea of lightning-making had never left us. Consequently, when we were told that lightning was made and exhibited at certain stated hours, in the unromantic district of Regent-street, we received the statement with some incredulity; and it was to test its truth that, after many years, we came to revisit the Polytechnic. Let us endeavour to give some account of what we learn from the lucid and interesting lecture, which explained to us the extraordinary performances of the great Induction Coil.

It was discovered by Faraday, many years ago, that a coil of wire, wound loosely round a magnet, became actively electric at the moment when the magnet was either placed within its folds or withdrawn from them, and also that a galvanic current, in passing round a conducting circuit, produces an "induced" current in another conductor that surrounds the first. A galvanic current is usually generated by what is called a galvanic battery, consisting of two dissimilar metals or other substances, technically named elements, not touching each other, but immersed in some acid fluid. Chemical action is excited, and electricity, in the form known as galvanism, is set free. If the elements are connected together, outside the acid, by a piece of wire, or any other conductor, the electricity will proceed from one element, called the positive pole of the battery, and will pass along the wire to the other or negative pole, thus making what is called a circuit. If the wire be interrupted, the electricity, if present in sufficient quantity, will leap across the gap in the form of a visible spark. If the gap be filled by. any substance capable of being chemically decomposed by electricity, the decomposition will take place. In all this we have only the galvanic