rickwork that can be employed, and I have no doubt that
in the future it will be frequently resorted to. Some of those examples
also show the introduction of cast ornaments, and others the employment
of carving as means of enriching the surface of brick walls with
excellent effect. Here we must leave the subject; but in closing, I
cannot forbear pointing to the art of the bricklayer as a fine example
of what may be accomplished by steady perseverance. Every brick in the
miles of viaducts or tunnels, houses, or public buildings, to which we
have made allusion, was laid separately, and it is only steady
perseverance, brick after brick, on the part of the bricklayer, which
could have raised these great masses of work. Let me add that no one
brick out of the many laid is of no importance. Some time ago a great
fire occurred in a public asylum, and about L2,000 of damage was done,
and the lives of many of the inmates endangered. When the origin of this
fire came to be traced out, it was found that it was due to one brick
being left out in a flue. A penny would be a high estimate of the cost
of that brick and of the expense of laying it, yet through the neglect
of that pennyworth, L2,000 damage was done, and risk of human life was
run. I think there is a moral in this story which each of us can make
out if he will.

* * * * *

A fireproof whitewash can be readily made by adding one part silicate of
soda (or potash) to every five parts of whitewash. The addition of a
solution of alum to whitewash is recommended as a means to prevent the
rubbing off of the wash. A coating of a good glue size made by
dissolving half a pound of glue in a gallon of water is employed when
the wall is to be papered.

* * * * *

PHENOMENA OF ALTERNATING CURRENTS.

[Footnote: From a paper read before the recent meeting of the American
Institute of Electrical Engineers, New York, and reported in the
_Electrical World_.]

By Prof. ELIHU THOMSON.

The actions produced and producible by the agency of alternating
currents of considerable energy are assuming greater importance in the
electric arts. I mean, of course, by the term alternating currents,
currents of electricity reversed at frequent intervals, so that a
positive flow is succeeded by a negative flow, and that again by a
positive flow, such reversals occurring many times in a second, so that
the curve of current of elec