Page:Popular Science Monthly Volume 6.djvu/460

444 a shallow pit scooped in the sand. A man was then put inside to shovel out the sand, and, as he dug, the curb sank around him. Presently he was waist-deep in water, and the well was finished and yielded freely all summer.



HE publication of Marey's "Animal Mechanism" in the "International Scientific Series" has put the general reader in possession of one of the most interesting works ever published on experimental physiology. The simplicity and precision of the author's experimental methods, his conscientiousness in being sure of one step before he takes the next, and the skill displayed in interpreting and combining his experimental results—all these admirable characteristics have rendered his book instructive and entertaining to those who merely follow from afar the progress of science, while, at the same time, he has furnished a model of precise research and clear exposition to the professed scientist.

Marey arrives at his facts directly, not inferentially, and this is the charm of his book. The mind of the reader does not rest on the fallible judgment or mere opinion of the author, but is brought face to face with the very records made by the phenomena themselves.

In studying the progress of science, one cannot help remarking certain periods of sudden acceleration in the progress of discovery. These periods of unusual activity are not always, but certainly are very often, due to the invention of some precise and readily-applicable instrument, which gives, as it were, a new scientific sense, and brings into the range of our intellectual vision phenomena and numbers whose existence were barely suspected, until revealed by the aid of some comparatively simple contrivance. Such epochs of sudden progress followed the inventions of the telescope, the spectroscope, the ophthalmoscope, the galvanometer, and the tuning-fork chronoscope. For the latter instrument, men of science are indebted to Dr. Thomas Young, that wonderful man, who touched no department of knowledge that he did not adorn. The application of the sinuous traces of a vibrating tuning-fork on a rolling cylinder, to divide a second of time into as many parts as the number of times the fork swings to and fro in a second, was described by Young in 1807, and published in his "Lectures on Natural Philosophy and the Mechanical Arts," vol. i., p. 191. Like Young's discoveries of the theory of colors, and of the undulatory theory of light, this beautiful invention laid fallow for many years, until reinvented in 1840 by Duhamel, and subsequently brought into general use in physics and physiology. It is now the 