With all this frugality, Franklin was not a miser; he abhorred the waste of money, not the proper use. His wealth increased rapidly. "I experienced too," he says, "the truth of the observation, 'THAT AFTER GETTING THE FIRST HUNDRED POUND, IT IS MORE EASY TO GET THE SECOND, money itself being of a prolific nature." He gave much unpaid public service and subscribed generously to public purposes; yet he was able, at the early age of forty-two, to turn over his printing office to one of his journeymen, and to retire from active business, intending to devote himself thereafter to such public employment as should come his way, to philosophical or scientific studies, and to amusements. From boyhood Franklin had been interested in natural phenomena. His "Journal of a Voyage from London to Philadelphia", written at sea as he returned from his first stay in London, shows unusual powers of exact observation for a youth of twenty. Many of the questions he propounded to the Junto had a scientific bearing. He made an original and important invention in 1749, the "Pennsylvania fireplace," which, under the name of the Franklin stove, is in common use to this day, and which brought to the ill-made houses of the time increased comfort and a great saving of fuel. But it brought Franklin no pecuniary reward, for he never deigned to patent any of his inventions. His active, inquiring mind played upon hundreds of questions in a dozen different branches of science. He studied smoky chimneys; he invented bifocal spectacles; he studied the effect of oil upon ruffled water; he identified the "dry bellyache" as lead poisoning; he preached ventilation in the days when windows were closed tight at night, and upon the sick at all times; he investigated fertilizers in agriculture. Many of his suggestions have since borne fruit, and his observations show that he foresaw some of the great developments of the nineteenth century. His fame in science rests chiefly upon his discoveries in electricity. On a visit to Boston in 1746 he saw some electrical experiments and at once became deeply interested. Peter Collinson of London, a Fellow of the Royal Society, who had made several gifts to the Philadelphia Library, sent over some of the crude electrical apparatus of the day, which Franklin used, as well as some contrivances he had purchased in Boston. He says in a letter to Collinson: "For my own part, I never was before engaged in any study that so engrossed my attention and my time as this has lately done."