Page:Popular Science Monthly Volume 6.djvu/470

454 We have thus obtained simultaneously the traces of the velocities of translation of the artificial bird, and the durations of the depressions of its wings, and we have obtained a series of determinations of which the preceding figure (4) furnishes some examples:

Experiment No. 1.—The upward indentation in the line a shows the duration of the depression of the wings. Taking that length on the scale of time, we see that the downward movement of the wing lasted less than $1⁄3$ of a second. In that experiment there was no translation of the bird. The line b does not show any indentation.

Experiment No. 2.—The duration of the depression of the wings (line a) is already greater; it exceeds one-half of a second. The translation was then nearly three metres per second. We find this by taking in the dividers the length on the line b of the $3 1⁄2$ double indentations of the tracer, which show that $3 1⁄2$ times $4⁄10$ of a metre, or 1.4 metre, have been traversed by the artificial bird. We carry this length to the scale of time, and we find that it is contained about twice in a second. We thus see at once that the duration of the downward motion of the wing increases with the velocity of translation of the artificial bird.

Experiments Nos. 3-6.—In the remaining experiments, proceeding as we have already done, we find that the duration of the depression of the wing increases with the velocity of translation, and that with a velocity of $5 1⁄2$ metres the downward movement of the wing lasts about one second. I have not been able to find the accurate relation between the velocity of translation and the duration of the downward motion of the wing. Experiments made in precisely the same conditions sometimes present slight differences, which are due to the fact that the slightest oscillation of the iron wire, which serves as a support and guide for the artificial bird, slightly changes the durations of the phenomena. From the first series of experiments, it would appear that the duration of the depression of the wing increases in proportion to the velocity of its translation, at least within the limits of the velocities with which I have experimented.



HERE are fields of labor in which women have been immemorially active. In all matters relating to the cares of the house and children among the civilized, and, among the barbarous and the lowest strata of life in Europe and elsewhere, field-labor, the care of animals, and the lighter manufactures, are the tasks imposed upon women. 