6 MEMORIE DELLA SOCIETÀ' 



3. Pinally it seems to be little more than a sninmary of the facts of observa- 

 tion already rehearsed to say that traces of a vortical action are found throughout 

 the spot, and especially in the umbra. The theory which regards cyclonic or vor- 

 tical action as a prominent agent in determining the forras we have stndied, ap- 

 pears then to be here in closer accordance with observation than the former. 



As the substance of the present article was written before Father Secchi's re- 

 marks appeared in the Angust Memorie it was originally prepared without re- 

 ference to the question raised there, and withont any special reference to the 

 cyclonic theory, and it is in no senso meant as a complete expression of opi- 

 nion on those several points in connection with which Father Secchi has done me 

 the honor to cite my name. As one of the few who have used an instrument of 

 adequate power in the particnlar field of research in which a large part of his 

 labors have lain, I am more able than most, perhaps to appreciate his eniinent 

 qnalities as an observer. Wheu however he states that longer stndy of the san 

 than I have yet given will change my views upon the theory of M. Faye, I may 

 remark that those views were not cmitted so hastily, or on snch light gronuds 

 as to be readily altered, for they were the result of several years of observation, 

 with an instrument of greater power than that Father Secchi employs. Doubtless 

 before adopting conclnsions in any way differing from those reached by one whose 

 ability as an observer deserves such respect, I was bonnd in every way to ve- 

 rify the grounds on which these conclnsions rested. If what seem to me the facts 

 of observation, conducted, and stili continue to conduct me, to views in many ways 

 differing from those which he maintains, in opposition to distinguished Italian 

 and French astronomers; I have less hesitation in trustiug to observations which 

 agree more nearly, with their views, from the belief that no pcrsonally cherished 

 hypothesis, has subjected me to that unconscious bias in the collection and in- 

 terpretation of facts, against which common experience shows that even eminent 

 ability is not a certain protection. (H). 



Allegheny, Pennsylvania, December 29 th , 1874. 



