his question over in his mind for several years, and arrived at the
conclusion that a house cast in one piece would be the answer. To
produce such a house involved the overcoming of many engineering and
other technical difficulties. These he attacked vigorously and disposed
of patiently one by one.

In this connection a short anecdote may be quoted from Edison as
indicative of one of the influences turning his thoughts in this
direction. In the story of the ore-milling work, it has been noted that
the plant was shut down owing to the competition of the cheap ore
from the Mesaba Range. Edison says: "When I shut down, the insurance
companies cancelled my insurance. I asked the reason why. 'Oh,' they
said, 'this thing is a failure. The moral risk is too great.' 'All
right; I am glad to hear it. I will now construct buildings that won't
have any moral risk.' I determined to go into the Portland cement
business. I organized a company and started cement-works which have
now been running successfully for several years. I had so perfected the
machinery in trying to get my ore costs down that the making of cheap
cement was an easy matter to me. I built these works entirely of
concrete and steel, so that there is not a wagon-load of lumber in them;
and so that the insurance companies would not have any possibility of
having any 'moral risk.' Since that time I have put up numerous factory
buildings all of steel and concrete, without any combustible whatever
about them--to avoid this 'moral risk.' I am carrying further the
application of this idea in building private houses for poor people, in
which there will be no 'moral risk' at all--nothing whatever to burn,
not even by lightning."

As a casting necessitates a mold, together with a mixture sufficiently
fluid in its nature to fill all the interstices completely, Edison
devoted much attention to an extensive series of experiments for
producing a free-flowing combination of necessary materials. His
proposition was against all precedent. All expert testimony pointed to
the fact that a mixture of concrete (cement, sand, crushed stone, and
water) could not be made to flow freely to the smallest parts of an
intricate set of molds; that the heavy parts of the mixture could not
be held in suspension, but would separate out by gravity and make
an unevenly balanced structure; that the surface would be full of
imperfections, etc.

Undeterred by the unanimity of adverse opinions, however