Wood, of the University of Wisconsin. Professor Wood, on repeating Mr. Clayden’s experiment, obtained dark flashes without any difficulty, but as they failed to appear when the light of an incandescent lamp was substituted for the electric spark, he concludes that there is something in the spark essential to the reversal. Dr. Lockyer summarizes his conclusion by saying that dark-lightning flashes “do not exist in Nature, but 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. * * * * *