their appearances on photographs are due to some chemical action which takes place in the gelatin film."
"Warming Up."—"Warming up" is the expressive term of general currency, which Dr. E. G. Lancaster adopts to denote the process in which one starting on any work in a little while suffers a short period of fatigue, from which he soon recovers, to go on with new and increased vigor. This occurs in the course of walks, with students engaged in earnest reading or in writing, and in animals, as in dogs on the chase, the animals pursued, and racehorses. "It is said of two famous trotters, each of which has reduced the world's record within a few years, that the period of warming up was very characteristic.… Athletes, especially ball players, realize the importance of practice just before the games, to be followed by a slight rest. A pitcher would hardly enter the box till he had got his arm in working order by a few minutes' practice. Orators often are dull at first, but warm up. It is said that Wendell Phillips was often hissed for his slow, uninteresting speech, but rallied to the occasion at such times with his masterly oratory." Dr. Lancaster has experimented on the phenomena, using a method like those of Mosso and of Lombard in the psychological laboratory at Clark University, and publishes the results, with details and curves, in the papers of the Colorado College Scientific Society. He tried ten or twelve subjects, experimenting on the middle finger of the right hand, and gaining most of his results from four or five persons. He finds that warming up is general, but not universal. One subject always did his best work first. He likewise showed no warming up in his mental work. The phenomenon called "second mind" is closely allied to warming up, but is not the same. The author is of the opinion that the importance of this process is greatly misunderstood.
Sixty Years' Improvements in Steamships.—A review of what has been accomplished in sixty years in the improvement of transatlantic traffic, given by Sir William H. White in his address at the British Association on Steam Navigation at High Speeds, shows that speed has been increased from eight and a half to twenty-two and a half knots an hour, and the time of the voyage has been brought down to about thirty-eight per cent of what it was in 1838. Ships have been more than trebled in length, about doubled in breadth, and increased tenfold in displacement. The number of passengers carried by a steamship has been enlarged from about one hundred to nearly two thousand. The engine power has been made forty times as great. The ratio of horse power to the weight driven has been quadrupled. The rate of coal consumption per horse power per hour is now only about one third what it was in 1840. Had the old rate of coal consumption continued, instead of three thousand tons of coal, nine thousand would have been required for a voyage at twenty-two knots. Had the engines been proportionately as heavy as those in use sixty years ago, they would have weighed about fourteen thousand tons. In other words, machinery, boilers, and coal would have exceeded the total weight of the Campania as she floats to-day. "There could not be a more striking illustration than this of the close relation between improvements in marine engineering at high speed. Equally true is it that this development could not have been accomplished but for the use of improved materials and structural arrangements."
American Advances in Forestry.—The Department of Agriculture having determined to prepare a book for the Paris Exposition, reviewing what has been accomplished in scientific agriculture in the United States, the Division of Forestry will contribute to it a short history of forestry in the United States, with an account of the efforts of private landholders to apply the principles of forestry. Much more has been accomplished in the United States in the way of forestry than has been supposed. Mr. Pinchot, the forester of the division, holds that wherever private owners have made the effort to use the merchantable timber on their woodland without injuring its productive power, and to establish new forests, there has been the intention of true forestry. The methods may have been imperfect, but