class="tdright">256

From a bust by Joseph, now in the library of Bell Rock Lighthouse. The Bell Rock Lighthouse, on the Eastern Coast
of Scotland 257 From the painting by Turner. The Bell Rock Lighthouse was
built by Robert Stevenson, grandfather of Robert Louis
Stevenson, on the Inchcape Reef, in the North Sea, near
Dundee, Scotland, in 1807-1810. The Present Lighthouse on Minot's Ledge, near
the Entrance of Massachusetts Bay, Fifteen
Miles Southeast of Boston 260 "Rising sheer out of the sea, like a huge stone cannon, mouth
upward."—Longfellow. The Lighthouse on Stannard Rock, Lake Superior 261 This is a stone-tower lighthouse, similar in construction to the
one built with such difficulty on Spectacle Reef, Lake Huron. The Fowey Rocks Lighthouse, Florida
264 Fourteen-Foot Bank Light Station, Delaware
Bay, Del. 268 The Great Beds Light Station, Raritan Bay, N. J. 270 A specimen of iron cylinder construction. A Storm at the Tillamook Lighthouse, in the
Pacific, one mile out from Tillamook Head,
Oregon 275 Saving the Cylinder of the Lighthouse at Smith
Point, Chesapeake Bay, from being Swamped
in a High Sea 279 When the builders were towing the unwieldy cylinder out to set
it in position, the water became suddenly rough and
began to fill it. Workmen, at the risk of their lives,
boarded the cylinder, and by desperate labours succeeded
in spreading sail canvas over it, and so saved a structure
that had cost months of labour and thousands of dollars. Great Waves Dashed Entirely Over Them, so that
They had to Cling for Their Lives to the
Air-Pipes 285 In erecting the Smith Point lighthouse, after the cylinder was
set up, it had to be forced down fifteen and a half feet
into the sand. The lives of the men who did this, working
in the caisson at the bottom of the sea, were absolutely
in the hands of the men who managed the engine
and the air-compressor at the surface; and twice these
latter were entirely deluged by the sea, but still maintained
steam and kept everything running as if no sea
was playing over them. Peter Cooper Hewitt 292 With his interrupter. Watching a Test of the Hewitt Converter 299 Lord Kelvin in the centre. The Hewitt Mercury Vapour Light 305 The circular piece just above the switch button is one form of
"boosting coil" which operates for a fraction of a second
when the current is first turned on. The tube shown
here is about an inch in diameter and several feet long.
Various shapes may be used. Unless broken, the tubes
never need renewal. Testing a Hewitt Converter 311 The row of incandescent lights is used, together with a voltmeter
and ammeter, to measure strength of current, resistance,
and loss in converting.

BOYS' SECOND BOOK OF
INVENTIONS

CHAPTER I
THE MIRACLE OF RADIUM
Story of the Marvels and Dangers of the New Element Discovered by Professor and Madame Curie

No substance ever discovered better deserves the term "Miracle of Science," given it by a famous English experimenter, than radium. Here is a little pinch of white powder that looks much like common table salt. It is one of many similar pinches sealed in little glass tubes and owned by Professor Curie, of Paris. If you should find one of these little tubes in the street you would think it hardly worth carrying away, and yet many a one of them could not be bought for a small fortune. For all the radium in the world to-day could be heaped on a single table-spoon; a pound of it would be worth nearly a million dollars, or more than three thousand times its weight in pure gold.

Professor and Madame Curie, who discovered radium, now possess the largest amount of any one, but there are small quantities in the hands of English and German scientists, and perhaps a dozen specimens in America, one owned by the American Museum of Natural History and several by Mr. W. J. Hammer, of New York, who was the first American to experiment with the rare and precious substance.