74 ALL ABOARD FOR SUNRISE LANDS.

ashore _stone weighing one or two tons. The keepers, poor fellows,
went with the wreck. When Minot’s Ledge was occupied again, they
gave up the pipe-stem style and built of stone, tier upon tier, solid
and true. As you can only work upon the ledge at a certain stage
of the tide, it took several seasons to prepare the foundation and lay
a few courses of granite. But it was finished at last, and a splendid
pile of granite it is.” ;

“Uncle, what is it they light up the lantern with?”

“Do you mean, Rick, how they do it? Let me go back some way.
There is at the mouth of the river Garonne in France, a lighthouse
nigh three hundred years old, and it is a fine structure. For a light,
at first they burnt pieces of oak in a chauffer or small furnace. That
was a common mode, and long practised. It seemed a wonderful ad-
vance, when over this little bonfire up in the lighthouse tower, a
rough reflector in the shape of an inverted cone was suspended and
prevented the upward passage of the light. In 1760, Smeaton, the
famous engineer of the LHddystone lighthouse, used wax candles.
In 1789, in the old Garonne lighthouse, a Frenchman, Lenoir, put
mirrors or reflectors near Argand lamps introduced into the lantern.
The Argand lamp has a circular wick and chimney. By-and-by,
in the present century, came Fresnel who made extensive improve-
ments, introducing what is called the lens principle. A lens is any
substance that will let the light through and refract or bend it.
For instance, when a piece of glass is convex as we say, or when’
it bulges out, that will so bend the image of an object as to enlarge
it. In telescopes and microscopes, we take advantage of this mag-
nifying principle, and the big lens in the lighthouse tower is so
constructed that the light of a lamp comparatively small is mag-
nified into the shining of a mammoth ball of fire, till it seems
like a new-risen sun above the dark surface of the sea. I have