=Destruction of Powder Magazines.=--Not less appalling is the devastation caused by lightning when it falls on a powder magazine. Here is a striking example: On the eighteenth of August, 1769, the tower of St. Nazaire, at Brescia, was struck by lightning. Underneath the tower about 200,000 pounds of gunpowder, belonging to the Republic of Venice, were stored in vaults. The powder exploded, leveling to the ground a great part of the beautiful city of Brescia, and burying thousands of its inhabitants in the ruins. It is said that the tower itself was blown up bodily to a great height in the air, and came down in a shower of stones. This is, perhaps, the most fearful disaster of the kind on record. But we are not without examples in our own times. In the year 1856 the lightning fell on the Church of St. John, in the Island of Rhodes. A large quantity of gunpowder had been deposited in the vaults of the church. This was ignited by the flash; the building was reduced to a mass of ruins, a large portion of the town was destroyed, and a considerable number of the inhabitants were killed. Again, in the following year, the magazine of Joudpore, in the Bombay Presidency, was struck by lightning. Many thousand pounds of gunpowder were blown up, five hundred houses were destroyed, and nearly a thousand people are said to have been killed.[24] =Experimental Illustrations.=--And now, before proceeding further, I will make one or two experiments, with a view of showing that the electricity of our machines is capable of producing effects similar to those produced by lightning, though immeasurably inferior in point of magnitude. Here is a common tumbler, about three-quarters full of water. Into it I introduce two bent rods of brass, which are carefully insulated below the surface of the water by a covering of india-rubber. The points, however, are exposed, and come to within an inch of one another, near the bottom of the tumbler. Outside the tumbler, the brass rods are mounted on a stand, by means of which I can send the full charge of this Leyden jar battery through the water, from point to point. Since water is a bad conductor of electricity, as compared with metals, the charge encounters great resistance in passing through it, and in overcoming this resistance produces considerable mechanical commotion, which is usually sufficient to shiver the glass to pieces.