ALEXANDER DALLAS BACHE. 



439 



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 over- 

 heated 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. Frazer, he determined with accuracy,, for the first time 

 in this country, the periods of the daily variations of the mag- 

 netic needle, and by another series of observations established 

 the connection between certain perturbations of the terrestrial 

 magnetism and the aurora borealis. With Prof. Courtenay he 

 investigated the magnetic dip at various places in the United 

 States, and with Mr. Espy made a minute survey of part of the 

 track of a tornado which visited New Jersey, June 19, 1835. 



After Stephen Girard died, in 1832, Prof. Bache was elected 

 one of the trustees of the College for Orphans, founded by the 

 will of the childless merchant. Three years later the trustees 

 decided to select a president for the institution, in order that 

 he might go abroad and study European methods of education 

 while other preparations were being made. Prof. Bache, then 

 only thirty years of age, was selected for the position. Al- 

 though regretting the consequent interruption of his scientific 

 researches, in which he had become much absorbed, he ac- 

 cepted the appointment, and departed on his mission, Sept. 30, 

 1836. His own previously published researches combined with 

 the memory of his distinguished ancestor to secure him a cordial 

 welcome by the intellectual class in each country that he visited. 

 Two years were spent agreeably and profitably in Europe, and 

 on his return Prof. Bache made a report to the trustees em- 

 bodying his observations on the schools of England, France, 

 Prussia, Austria, Switzerland, and Italy, with the many helpful 



