Page:Popular Science Monthly Volume 40.djvu/709

Rh that price. It was a light task to learn all that was in it." One can not forbear to moralize over this intense desire for knowledge, for what would not such a boy have learned with proper encouragement and opportunity! It must be to these and the succeeding years of hampered effort that Ferrel refers in a few sad words at the close of his narrative: "Much of my time has been wasted, especially the earlier part of it, because, not having scientific books and scientific associations, I often had nothing on hand in which I was specially interested."

It may be said that Ferrel began his career as an investigator in 1832, when on going out one day to work he noticed that the sun was eclipsed. He had not known that such an event was to occur, but it set him to thinking. He had somewhere learned the cause of solar and lunar eclipses, but his materials for further study were only a German calendar, such as farmers use, and a copy of Adams's Geography, with an appendix giving problems on the use of the globes. From these he found that the sun and moon moved with unequal velocities in different parts of their orbits, and that the fastest and slowest motions were at opposite points. Of this he writes: "My theory was that the earth and the moon moved with uniform velocity in circular orbits, and that these orbits were eccentrically situated with regard to the sun and earth. With regard to the moon's path, I knew that it crossed the ecliptic, but I did not know at what angle, and I also at first supposed that the node was fixed. At the beginning of the next year, when the next calendar came to hand, I discovered from the predicted eclipses that the node must recede. I saw from the calendars that there was some cycle of nineteen years, and suspected that this had something to do with the moon's node. This would make the node recede about 19° in a year, as the next year's eclipses seemed to require." Then, with the aid of some older calendars, Ferrel, about at the age of sixteen, proceeded to make out tables of the dates of eclipses in an empirical fashion, but he unfortunately assumed that the diameter of the earth's shadow was constant. "Upon this assumption I spent a vast amount of time, but could get no positions of the nodes or inclination of the orbit which would satisfy the eclipses. The amount of study I gave to the subject both day and night was very great, but I at last gave the matter up in despair. Some time after I was at work one day toward evening on the thrashing-floor, and saw the shadow of a distant vertical plank against the wall; I observed that it was much smaller than the width of the plank, and the reason for it occurred to me at once. I then saw the error of my assumptions with regard to the earth's shadow in my eclipse investigations and was now very anxious to go over again all my computations with the true diameter of the earth's shadow, for, knowing the