aterial, hence no
sediment short-circuits. 2. No jar breakage. 3. Possibility of quick
disconnection or replacement of any cell without employment of skilled
labor. 4. Impossibility of "buckling" and harmlessness of a dead
short-circuit. 5. Simplicity of care required. 6. Durability of
materials and construction. 7. Impossibility of "sulphation." 8. Entire
absence of corrosive fumes. 9. Commercial advantages of light weight.
10. Duration on account of its dependability. 11. Its high practical
efficiency.

XIX. EDISON'S POURED CEMENT HOUSE

THE inventions that have been thus far described fall into two
classes--first, those that were fundamental in the great arts and
industries which have been founded and established upon them, and,
second, those that have entered into and enlarged other arts that were
previously in existence. On coming to consider the subject now under
discussion, however, we find ourselves, at this writing, on the
threshold of an entirely new and undeveloped art of such boundless
possibilities that its ultimate extent can only be a matter of
conjecture.

Edison's concrete house, however, involves two main considerations,
first of which was the conception or creation of the IDEA--vast and
comprehensive--of providing imperishable and sanitary homes for
the wage-earner by molding an entire house in one piece in a single
operation, so to speak, and so simply that extensive groups of such
dwellings could be constructed rapidly and at very reasonable cost. With
this idea suggested, one might suppose that it would be a simple matter
to make molds and pour in a concrete mixture. Not so, however. And here
the second consideration presents itself. An ordinary cement mixture is
composed of crushed stone, sand, cement, and water. If such a mixture
be poured into deep molds the heavy stone and sand settle to the bottom.
Should the mixture be poured into a horizontal mold, like the floor of
a house, the stone and sand settle, forming an ununiform mass. It was
at this point that invention commenced, in order to produce a concrete
mixture which would overcome this crucial difficulty. Edison, with
characteristic thoroughness, took up a line of investigation, and after
a prolonged series of experiments succeeded in inventing a mixture that
upon hardening remained uniform throughout its mass. In the beginning
of his experimentation he had made the conditions of test very severe by
the construction of forms simi