ii4 THE POPULAR SCIENCE MONTHLY. 



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 Pennsyl- 

 vania. 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 appar- 

 ently a remote prospect, for he had only the stinted pay of a lieu- 

 tenant 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 suc- 

 cessful 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 in- 

 quiries and experiments, the latter not unattended with danger, 

 " the most frequent cause of explosion was found to be the grad- 

 ual 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 va- 

 rious researches in pure science in co-operation with his fellow- 

 members. 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 



