362 EULOGY ON PROFESSOR ALEXANDER DALLAS BACHE. 



nent at almost every stage of the investigation ; and in some instances 

 explosions were produced which alarmed the neighborhood. So true 

 is it that in the pursuit of science dangers are oftentimes voluntarily- 

 encountered, exactingno less courage or firmness of nerve than that which 

 animates the warrior in the more conspicuous but scarcely more import- 

 ant conflicts of the battle-field. 



The attention of Mr. Bache at this period was not exclusively devoted 

 to his labors in connection with the Franklin Institute. He was also a 

 member of the American Philosophical Society, and, as such, in associ- 

 ation with Hare, Espy, and others interested in the pursuit of various 

 branches of physics and chemistry. He erected an observatory in the 

 yard of his dwelling, in which, with the aid of his wife and of his for- 

 mer pupil, John E. Eraser, he determined with accuracy, for the first 

 time in this country, the periods of the daily variations of the magnetic 

 needle, and by another series of observations the connection of the fit- 

 ful variations of the direction of the magnetic force with the appear- 

 ance of the aurora borealis. 



Again, in connection with his friend, Mr. Espy, he made a minute 

 survey of a portion of the track of a tornado, which visited New Bruns- 

 wick, in New Jersey, on the 19th of June, 1835, and from the change of 

 place and relative position of the trees aud other objects, as left by the 

 wiud, he succeeded in establishing the fact, in accordance with the 

 hypotheses of Mr. Espy, that the effects of the storm were due to an 

 ascending and progressive column of air, by which all objects within 

 the influence of the disturbance, on either side the track, were drawn 

 inward, and not due, as had been supposed, to a horizontal rotation at 

 the surface, which would tend to throw them outward by centrifugal 

 projection. In cooperation with Professor Courtenay, he also made a 

 series of determinations of the magnetic dip at various places in the 

 United States. Indeed, terrestrial magnetism was with him a favorite 

 subject, to which he continued to make valuable contributions at inter- 

 vals during his whole life. The phenomena of heat likewise engaged 

 much of his attention, and he was the first to show, contrary to gener- 

 ally-received opinion, that the radiation and consequent absorption of 

 dark heat is not affected by color. His investigations in this line were 

 suddenly brought to a close by an accident, which we may be allowed 

 to mention as furnishing an illustration of his self-control and consid- 

 erate regard for the feelings of others. After an expenditure of money 

 which he could ill afford, and of time withdrawn from the hours due to 

 repose, he had procured and arranged on a stand a series of delicate 

 instruments intended for a long-meditated experiment on radiant heat. 

 During his temporary absence his mother, in hurriedly passing through 

 the apartment, accidentally caught in her dress the support of the 

 apparatus and brought the whole to the floor, a mass of mingled frag- 

 ments. The author of this disaster was so painfully affected by the 

 destruction, of which she had been the unintentional cause, as to be 



