A few years later, in March, 1796, the Lowestoffe was struck in the Mediterranean, and we read as follows in the log of the ship: “North end of Minorca; heavy squalls; hail, rain, thunder, and lightning. 12.15, ship struck by lightning, which knocked three men from the masthead, one killed. 12.30, ship again struck; main top-mast shivered in pieces; many men struck senseless on the decks. Ship again struck, and set on fire in the masts and rigging; mainmast shivered in pieces; fore top-mast shivered; men benumbed on the decks, and knocked out of the top; one man killed on the spot. 1.30, cut away the mainmast; employed clearing wreck. 4, moderate; set the foresail.”[22]
Again, in 1810, the Repulse, a ship of seventy-four guns, was struck, off the coast of Spain. “The wind had been variable in the morning—and at 12.35 there was a heavy squall, with rain, thunder, and lightning. The ship was struck by two vivid flashes of lightning, which shivered the maintop-gallant mast, and severely damaged the mainmast. Seven men were killed on the spot; three others only survived a few days; and ten others were maimed for life. After the second discharge the rain fell in torrents. The ship was more completely crippled than if she had been in action, and the squadron, then engaged on a critical service, lost for a time one of its fastest and best ships.”[23]
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.
To charge the battery will take about twenty turns of this large Holtz machine. Observe how the pith ball of the electroscope rises as the machine is worked, showing that the charge is going in. And now it remains stationary; which is a sign that the battery is fully charged, and can receive no more. You will notice that the outside coating of the battery has been already connected with one of the brass rods dipping into the tumbler of water. By means of this discharger I will now bring the inside coating into connection with the other rod. And see, before contact is actually made, the spark has leaped across, and our tumbler is violently burst asunder from top to bottom.
GLASS VESSEL BROKEN BY DISCHARGE OF LEYDEN JAR BATTERY.
This will probably appear to you a very small affair, when compared with the tearing asunder of solid masonry, and the hurling about of stones by the ton weight. No doubt it is; and that is just one of the lessons we have to learn from the experiment we have made. For, not only does it show us that effects of this kind may be caused by electricity artificially produced, but it brings home forcibly to the mind how incomparably more powerful is the lightning of the clouds than the electricity of our machines.
The property which electricity has of setting fire to combustible substances may be easily illustrated. This india-rubber tube is connected with the gas pipe under the floor, and to the end of the tube is fitted a brass stop-cock which I hold in my hand. I open the cock, and allow the jet of gas to flow toward the conductor of Carré’s machine, while my assistant turns the handle; a spark passes, and the gas is lit. Again, my assistant stands on this insulating stool, placing his hand on the large conductor of the machine, while I turn the handle. His body becomes electrified, and when he presents his knuckle to this vessel of spirits of wine, which is electrically connected with the earth, a spark leaps across, and the spirits of wine are at once in a blaze. Once more; I tie a little gun-cotton around one knob of the discharging rod, and then use it to discharge a small Leyden jar; at the moment of the discharge the gun-cotton is set on fire.
It would be easy to explode gunpowder with the electric spark, but the smoke of the explosion would make the lecture-hall very unpleasant for the remainder of the lecture. I propose, therefore, to substitute for gunpowder an explosive mixture of oxygen and hydrogen, with which I have filled this little metal flask, commonly known as Volta’s pistol. By a very simple contrivance, the electric spark is discharged through the mixture, when I hold the flask toward the conductor of the machine. A cork is fitted tightly into the neck of the flask, and at the moment the spark passes you hear a loud explosion, and you see the cork driven violently up to the ceiling.