Gunpowder was discovered from the falling of a spark on some materials mixed in a mortar. Electricity was discovered by a person observing that a piece of rubbed glass attracted small bits of paper. Thales, of Miletus (600 B.C.), noted this with amber. Musical notation was discovered by an Egyptian observer noticing the different ring of blacksmiths' hammers. The beautiful capitol of a Corinthian column was discovered by an Athenian in his garden noticing a slab of stone placed accidentally upon a basket. I think we owe the telescope to the children of a spectacle-maker in Germany, who, for amusement, looked through two or more pairs of spectacles to the distant sky. The microscope was naturally the reverse of the telescope, and followed down step by step to its present state of improvement;—for when man once perceives any secret in nature he is endowed with the power, for his own good, of following it out to the uttermost. Nothing is therefore too little for man's attention. A 6,000-ton steamer, or a great war-ship, are instances of man practically applying his discoveries. Would it not be absurd to say that man invented a great steamship, with all its steam and electric marvels? I should say that a steamship, or a railroad, or the electric telegraph, or telephone are fully as much guided by great natural laws as the formation of the hexagon cells of the honeycomb. I shall show later on how ridiculous and absurd Darwin's account of this cell-formation by natural selection really is. Vaccination for smallpox was discovered by one of our medical men observing that milkmaids in the country districts were free from the disease. A few drops of aquafortis fell accidentally on the spectacles of a Nuremberg cutler, and the process of etching upon glass was revealed. The dew one night rusted the gun-barrrel of a sentry, and since then mezzotints have delighted the eyes of men. The process of lithographing was perfected by purely accidental circumstances. A poor musician was anxious to know whether music could not be etched upon stone as well as upon copper. He had just prepared a slab when his mother, who evidently did not profit by his art, asked him to make a memorandum of some clothes to be washed. Neither pen nor paper being at hand, he wrote the list on the stone with an etching preparation, intending to make a copy at a more convenient time. When about to clean off the stone he wondered what effect aquafortis would have upon it. The application of the acid made the writing stand out in relief. He found he could make a perfect impression by inking the stone.