Page:Popular Science Monthly Volume 40.djvu/710

690 of the moon and the angular diameter of the sun, I was able to determine this. As soon as I could find time I went over the whole work, and everything came out as satisfactory as could reasonably be expected with my methods. . . . This was in the winter of the first part of 1834. I now ventured to predict by my method the eclipses for the next year, 1835. I determined that there would be three eclipses—two of the moon and one of the sun. . . . I made a record of the whole in a book and awaited for the next calendar for comparison with its predictions. All the circumstances of the lunar eclipses agreed remarkably well, and the greatest error in the predicted times was only nine minutes.'* And this was the work of a farmer's boy, without help, without encouragement, in the time that he could spare from daily work!

His next book seems to have been Gummere's Surveying, which he mastered in the spring of 1834, with the exception of the miscellaneous examples at the end of the volume, for which no rules had been given and which required a knowledge of geometry. "During the summer, as I had a little time to spare, I dwelt upon these, giving weeks sometimes to a single proposition. It happened that during the summer I was engaged a good part of my time on the thrashing-floor, which had large doors at both ends with wide and soft poplar planks. Upon these I made diagrams, describing circles with the prongs of large pitchforks, and drawing lines with one of the prongs and a piece of board. One by one I mastered all the problems in this way except three. For more than a quarter of a century these diagrams were visible on the doors, and, in returning occasionally to the old homestead, I always went to take a look at them."

This kind of home study continued until 1839, when Ferrel went to Marshall College, at Mercersburg, Pa. Here he learned algebra, geometry, and trigonometry, and gave some time also to Latin and Greek. The next winter he taught near home; but in 1840 he returned to Marshall It was in this year that one of his professors assigned original problems in mathematics to the class. "On one occasion he gave the problem: Given the distances of a well from the three angles of an isosceles triangle, to determine the triangle. . . . This was easy to me at the time, for it was one of the problems which I had solved while at work on the thrashing-floor, with the use of diagrams on the barn doors, before I had seen a college or a treatise on algebra or geometry."

His money was exhausted in the latter part of 1841, and he went home to teach for two years. Bethany College was then opened in Virginia, and he was admitted to the senior class, and graduated in 1844. It is curious to notice that during all these years there is no mention of apparatus, experiments, or systematic