A. Hall on the application of Photography, ete. 25 
with its “amoeba” or pseudopodial dissolution, when treating 
; relia.” 
of the so-called “* Paramecium Au 
(To be continued.] 
Art. V.—On the application of Photography to the determination 
of Astronomical data; by ASAPH HALL.* 
ANY one who has witnessed a total eclipse of the sun must 
have felt his utter inability to make a correct description of the 
various features of the phenomenon, and must have wished for 
some means by which all these features, so suddenly and so 
grandly displayed, might be portrayed impartially and truth- 
fully and in such a way that they could be subjected to a cool 
and leisurely examination. Such a means is furnished in a 
good degree by photography. A few photographs of the corona 
and protuberances of a total eclipse are far more trustworthy 
than all the hand sketches that have ever been made. It is 
aeeet does not yet appear to be clearly established. In the 
ope of provoking discussion and investigation of the subject a 
brief review of what has been done in this application of the 
photographic method seems opportune, especially so, consider- 
ing the extensive use that ma: be made of the method in observ- 
ing the transit of Venus now near at hand. 
SS # Read before the Washington Philosophical Society. 
