690 THE POPULAR SCIENCE MONTHLY, 



tance of tlie moon and the angular diameter of the snn, 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 

 reasonahly 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 mis- 

 cellaneous 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 hap- 

 pened 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 draw- 

 ing 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 ge- 

 ometry." 



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 



