How much goes to sound observing is thus stated by John Stuart Mill,--“The observer is not he who merely sees the thing which is before his eyes, but he who sees what parts the thing is composed of. One person, from inattention, or attending only in the wrong place, overlooks half of what he sees; another sets down much more than he sees, confounding it with what he imagines, or with what he infers; another takes note of the _kind_ of all the circumstances, but being inexpert in estimating their degree, leaves the quantity of each vague and uncertain; another sees indeed the whole, but makes such an awkward division of it into parts, throwing into one mass things which require to be separated, and separating others which might more conveniently be considered as one, that the result is much the same, sometimes even worse than if no analysis had been attempted at all.” How an explorer of ability may witness a new fact without realizing that it points to a great industry, is shown in the case of Lord Dundonald. In 1782, or thereabout, near Culross Abbey in Scotland, he built a tar-kiln. Noticing the inflammable nature of a vapor arising during the distillation of tar, the Earl, by way of experiment, fitted a gun-barrel to the eduction pipe leading from the condenser. On applying fire to the muzzle, a vivid light blazed forth across the waters of the Frith, distinctly visible on the opposite shore. Soon afterward the inventor visited James Watt at Handsworth, near Birmingham, and told him about the gas-lighting at the kiln, but his host paid no attention to the matter. His assistant, William Murdock, however, was impressed by the story, and some years later applied gas to the illumination of the Soho works where Watt’s engines were built. This was the beginning of gas-lighting as a practical business.