An invention to make smoke go the wrong way in a chimney might be a very ingenious thing, but it would be of no use to humanity.

The patent office at Washington is full of wonderful devices of ingenious mechanism, but not one in hundreds is of use to the inventor or to the world.

And yet how many families have been impoverished, and have struggled for years amid want and woe, while the father has been working on useless inventions.

A.T.Stewart, as a boy, lost eighty-seven cents, when his capital was one dollar and a half, in buying buttons and thread which shoppers did not call for.

After that he made it a rule never to buy anything which the public did not want, and so prospered.
An observing man, the eyelets of whose shoes pulled out, but who could not afford to get another pair, said to himself, "I will make a metallic lacing hook, which can be riveted into the leather." He was then so poor that he had to borrow a sickle to cut grass in front of his hired tenement.