290 
Aus den Ergebnissen des genannten Verfassers sind (teils von 
ihm selbst, teils von anderen) Folgerungen gezogen worden, aus 
denen erhellt, daß man jenen Ergebnissen, wenn auch nicht in 
bezug auf die numerischen Details, so doch in bezug auf den qua- 
litaven Inhalt jener, eine allgemeine Gültigkeit zugeschrieben hat, 
die ihnen nicht zukommt. Diese Folgerungen betreffen einesteils 
physiologische Fragen, anderenteils Regeln rationellen Verfahrens 
bei Anstellung und Bearbeitung von Messungen mit okkultierenden 
Mikrometern. 
So liest man z. B. auf S. 10. der zitierten Abhandlung die fol¬ 
genden Betrachtungen: 
„(The abovei leaves, it seems, no doubt that while the stars, without respect 
to their magnitude, vanish to the sight simultaneously with their occultation, they 
do not reappear simultaneously with their emersion from the occulting body. 
The eye must therefore require a certain time before the impression of light can 
be transferred to the brain, and the length of this time is dependent on the in¬ 
tensity of light emitted by the star.It seems reasonable to conclude, that 
the time which elapses between the entrance of the light into the eye and its 
perception by the brain is mainly consumed in forming the image on the retina. 
The process is probably analogous to that which takes place on the sensitive 
plate in a photographic camera, in which, as we know, the time for the forma¬ 
tion of the image depends upon the intensity of the light. Physiologists are also 
now cognizant of the fact, that the formation of the image on the retina is not 
momentary. It is true that Prof. H. von Helmholtz says in his Handbuch der 
physiologischen Optik, Leipzig 1892, p. 180, that „„It has not hitherto been de¬ 
monstrated, that the perception takes place later than the light begins to act, 
but on the other hand it may last after the light has ceased to act““. When 
Prof. Helmholtz expressed himself thus, he probably alluded to 
light in general and not to light in such faint quantities, as are 
here in question. In connection with what has been said about 
the stars, that without regard to their magnitude, they vanish 
simultaneously with their passing behind a screen, I must re¬ 
mark, that although a strong light leaves its impression on the 
eye for a shorter or longer time after the source of the light is 
removed, 1 have not been able to perceive anything of this kind 
in the numerous observations made with my refractor, with great care and with 
special regard for this phenomenon“. 
Solche Folgerungen über die Natur des physiologischen Prozesses, 
sowie auch die Bemerkung, wonach der von v. Helmholtz ausge- 
sprochene physiologische Satz, soweit schwache Lichtquellen in 
Frage kommen, durch die astronomischen Beobachtungen nicht be¬ 
stätigt wird, verlieren ihre Stichhaltigkeit, sobald es sich heraus¬ 
gestellt hat, daß die von Herrn Pihl gefundenen Tatsachen nicht ein 
