Sir Richard Arkwright, the inventor of the spinning jenny, though a man of great personal strength, suffered from wretched health.

James Watt, the inventor of the steam engine, was continually ailing until he approached old age. He had a prodigious memory and as an inventive genius he has never been surpassed.

Ill health and failing eyesight forced Joseph Niepce to retire from the army at the age of twenty-eight. It was during this opportune leisure that the idea of obtaining sun-pictures first suggested itself to him. In 1826 he learnt that Daguerre was working on the same lines and three years later they cooperated in order to perfect what was, however, Niepce’s discovery.