ment became alarmed at the fearful destruction of ship timber in its dock-yards by a minute boring beetle, and applied to him for a remedy. He replied that the beetle which laid the eggs only appeared in the month of May, and that by submerging the timber during that period it could be protected from its ravages. The Government did so, and thus not only saved its timber at an insignificant expense, but also brought the derided bug-hunter into respect, as one who had demonstrated the practical utility of his apparently visionary study.
Researches upon the properties of laughing-gas and ether and investigations relating to the peculiarities of infusorial life also exhibit knowledge which at first appeared absolutely worthless, but was afterward found to be exceedingly practical. Students originally took ether for fun, and laughing-gas fell to the level of a wonder exhibited by itinerant lecturers; yet out of that knowledge was destined to come our modern discovery of anæsthesia, by which surgical operations may be performed without pain and without the knowledge of the sufferer. In like manner the researches upon the infusoria, from the time of Leuwenhoek to Ehrenberg, had apparently no practical value, yet from their discoveries have been developed a truer form of one of the most important practical doctrines of modern chemistry, a modification of the practice of medicine, a revolution of the science of surgery, an application of new and more correct ideas in matters pertaining to agriculture; and, combined with all this, remains the probability that their power for usefulness is not yet exhausted.
For the sake of illustrating the difference between the practical man and theorist, let us suppose two persons to visit the northern peninsula of Michigan seeking for iron. The one runs along blindly, takes up with every good show, and mines. The result is, he either makes a happy strike by mere accident, or spends thousands of dollars in useless search. The other has studied the laws of electricity, and knows that certain ores of iron are magnetic. He understands also that these ores will exert their influence through any amount of superincumbent earth. Consequently he provides himself with a dipping-needle and compass, and by the operation of these tells where a bed is located, its approximate depth, and probable amount of material. To prevent being deceived by the magnetic schists in that region, by means of his dipping-needle and compass he traces up the bed until he finds an outcrop. Thus have been located, at little expense, many of the mining regions of that locality. What an achievement is this, and how much better than the blind guesses of the so-called practical man!
The history of that wonderful piece of mechanism, the steam engine, furnishes another illustration of a different character. In
