Two of the men prostrated by the gas were sent to a hospital in New York, where they were months in recovering. Another went insane. Griffin was blind for three weeks. Four other caisson-men came out of the work with the painful malady known as "bends," which attacks those who work long under high air-pressure. A victim of the "bends" cannot straighten his back, and often his legs and arms are cramped and contorted. These terrible results will give a good idea of the heroism required of the sea-builder. Having sunk the caisson deep enough the workmen filled it full of concrete and sealed the top of the air-shaft. Then they built the light-keeper's home, and the lantern was ready for lighting. Three days within the contract year the tower was formally turned over to the Government. And thus the builders, besides providing a warning to the hundreds of vessels that yearly pass up the bay, erected a lasting monument to their own skill, courage, and perseverance. As long as the shoal remains the light will stand. In the course of half a century, perhaps less, the sea-water will gnaw away the iron of the cylinder, but there will still remain the core of concrete, as hard and solid as the day on which it was planted. It is fitting that work which has drawn so largely upon the highest intellectual and moral endowments of the engineer and the builder should not serve the selfish interests of any one man, nor of any single corporation, nor even of the Government which provided the means, but that it should be a gift to the world at large. Other nations, even Great Britain, which has more at stake upon the seas than any other country, impose regular lighthouse taxes upon vessels entering their harbours; but the lights erected by the United States flash a free warning to any ship of any land. [Illustration: Peter Cooper Hewitt. _With his interrupter._] CHAPTER IX THE NEWEST ELECTRIC LIGHT _Peter Cooper Hewitt and His Three Great Inventions--The Mercury Arc Light--The New Electrical Converter--The Hewitt Interrupter_