year from 1835 to 1841, and never out of danger of arrest.

In a small house in Philadelphia, in the winter of 1834--35, he began
his investigations. He melted his gum by the domestic fire, kneaded it
with his own hands, spread it upon a marble slab, and rolled it with a
rolling-pin. A prospect of success flattered him from the first and
lured him on. He was soon able to produce sheets of India-rubber which
appeared as firm as those imported, and which tempted a friend to
advance him a sum of money sufficient to enable him to manufacture
several hundred pairs of shoes. He succeeded in embossing his shoes in
various patterns, which gave them a novel and elegant appearance.
Mindful, however, of the disasters of the Roxbury Company, he had the
prudence to store his shoes until the summer. The hot days of June
reduced them all to soft and stinking paste. His friend was
discouraged, and refused him further aid. For his own part, such
experiences as this, though they dashed his spirits for a while,
stimulated him to new efforts.

It now occurred to him, that perhaps it was the turpentine used in
dissolving the gum, or the lampblack employed to color it, that
spoiled his product. He esteemed it a rare piece of luck to procure
some barrels of the sap not smoked, and still liquid. On going to the
shed where the precious sap was deposited, he was accosted by an
Irishman in his employ, who, in high glee, informed him that he had
discovered the secret, pointing to his overalls, which he had dipped
into the sap, and which were nicely coated with firm India-rubber. For
a moment he thought that Jerry might have blundered into the secret.
The man, however, sat down on a barrel near the fire, and, on
attempting, to rise, found himself glued to his seat and his legs
stuck together. He had to be cut out of his overalls. The master
proceeded to experiment with the sap, but soon discovered, that the
handsome white cloth made of it bore the heat no better than that
which was produced in the usual manner.

It is remarkable, that inventors seldom derive direct aid from the
science of their day. James Watt modestly ascribes to Professor Black
part of the glory of his improvements in the steam-engine; but it
seems plain from his own narrative, that he made his great invention
of the condenser without any assistance. Professor Black assisted to
instruct and form him; but the flash of genius, which made the
steam-engine what we now see it, was