He was especially fond of wandering along the seashore, and observing and examining the many curious and mysterious objects which he found on the crags and in the sand. One day his eye was struck with the bladders of seaweed, which he found full of air. The question was, how did the air get into them? This puzzled him, and he could find no answer to it, because he had no instruments to experiment with.
But on another day, soon after, as he strolled on the beach, what was his surprise and delight to find a case of surgical instruments, which had been flung up from some wreck on the coast! Armed with this, he hastened home, and managed to turn each one of the instruments to some useful account. He constructed an air-pump out of a surgeon's syringe, and made a great many experiments with it.
Fortunately for Humphry, he formed a friendship with a youth who could not only sympathize with him, but was of a great deal of use to him. This was Gregory Watt, a son of the great James Watt, the inventor of the steam-engine. Gregory Watt had gone to Penzance for his health, and had there fallen in with the ambitious son of the wood-carver. This new friend was able to give Humphry many new and valuable hints and encouraged him with hopeful words to go on with his studies and experiments.
Already Humphry was getting to be known as a scientific genius beyond the quiet neighborhood of Penzance. He had proposed a theory on heat and light which had attracted the attention of learned men; and at twenty-one he had discovered the peculiar properties of nitrous oxide—what we now call "laughing-gas"—though he nearly killed himself by inhaling too much of it. He had also made many experiments in galvanism, and had found silicious earth in the skin of reeds and grass.
So famous indeed had he already become, that at the age of twenty-two—when most young men are only just leaving college—he was chosen lecturer on science at the great Royal Institution in London. There he amazed men by the eloquence and clearness with which he revealed the mysteries of science. He was so bright and attractive a young man, moreover, that the best London society gladly welcomed him to its drawing-rooms, and praises of him were in every mouth. His lecture-room was crowded whenever he spoke.
But he was not a bit spoiled by all this flattery and homage. He worked all the harder; resolved to achieve yet greater triumphs in science than he had yet done. An opportunity soon arose to turn his knowledge and inventive powers to account in a very important way. For a long time the English public had every now and then been horrified by the terrible explosions which took place in the coal mines. These explosions resulted often in an appalling loss of human life. Their cause was the filling of the mine by a deadly gas, called "fire-damp," which, when ignited by a lighted candle or lamp, exploded with fearful violence. One day an explosion of fire-damp occurred which killed over one hundred miners on the spot.
This event called universal attention to the subject, and Humphry Davy was besought to try and find some means of preventing, or at least lessening, similar calamities. He promptly undertook the task, and set about it with all his wonted energy. The problem before him was how to provide light in the mines in such a way that the miners might see to work by it, and at the same time be safe from the danger of fire-damp explosion. Many attempts had been made to achieve this, but they had all failed,
Davy began his experiments. He soon made several valuable discoveries. One was that explosions of inflammable gases could not pass through long narrow metallic tubes. Another was that when he held a piece of wire gauze over a lighted candle, the flame would not pass through it. As a result of his long and patient toil Davy was able at last to construct his now famous Safety-Lamp, which has undoubtedly saved the lives of thousands during the period which has elapsed since it was invented. He presented a model of his new lamp to the Royal Society, in whose rooms in London it is to be seen to this day.
It is a simple affair, being merely a lamp screwed on to a wire gauze cylinder, and fitted to it by a tight ring. His idea was to admit the fire-damp into the lamp gradually by narrow tubes, so that it would be consumed by combustion. The Safety-Lamp was in truth the greatest triumph of Humphry Davy's useful life.
"I value it," he said, "more than anything I ever did."