Page:Popular Science Monthly Volume 48.djvu/124

114 him in his usual state of calm deportment. These ebullitions were, however, of rare occurrence, and always of short duration."

On graduating, Lieutenant Bache was assigned to duty at the academy as assistant professor. A year later he was transferred at his own request to engineering service on the fortifications at Newport, R. I., under Major (afterward General) J. G. Totten. Here he remained two years. One of his recreations during this period was making a collection of shells of mollusks.

In 1828, being then twenty-two years of age. Lieutenant Bache resigned his commission in the army to accept a call to the chair of Natural Philosophy and Chemistry at the University of Pennsylvania. This change was welcome in more ways than one. He was engaged to Miss Nancy Clarke Fowler, the daughter of an old and highly respected citizen of Newport, but marriage was apparently a remote prospect, for he had only the stinted pay of a lieutenant of engineers, out of which he must contribute to the support of his mother and her younger children. The salary of his new position, however, justified him in hastening the happy event.

His year's experience in teaching at West Point assisted Mr. Bache in taking up his duties at the university. He was a very successful instructor, and popular with his students. But he did not rest content with imparting knowledge obtained by the labors of others. He joined the Franklin Institute, then newly established, and took a prominent part in its investigations for the promotion of the mechanical arts.

For a full account of his labors in connection with this society we must here be content with referring to the volumes of its Journal from 1828 to 1835 inclusive. One of the most important and fruitful of these was the investigation of the bursting of steam boilers, of which he was the principal director. From inquiries and experiments, the latter not unattended with danger, "the most frequent cause of explosion was found to be the gradual heating of the boiler beyond its power of resistance; and, next to this, the sudden generation of steam by allowing the water to become too low, and its subsequent contact with the overheated metal of the sides and other portions of the boiler. The generation of gas from the decomposition of water as a cause of explosion was disproved, as was also the dispersion of water in the form of spray through superheated steam."

Early in 1829 Mr. Bache was elected to membership in the American Philosophical Society, and at once entered upon various researches in pure science in co-operation with his fellowmembers. With the aid of his wife and of his former pupil, John F. Fraser, he determined with accuracy, for the first time in this country, the periods of the daily variations of the magnetic