( 162. } 
Of these experiments three always gave constant results, and pro- 
duced respectively ZB. stutzert NEUMANN and LEHMANN, B. denitro- 
fluorescens n. sp. and B. vulpinus n. sp. 
2nd 2B. stutzeri deserves attention on account of the unique structure 
of its colonies, as seen in Fig. 1—5 on our Plate. 
3rd B. denitrojluorescens is the first example of a denitrifying, non 
liquefying fluorescent. 
4 B vulpinus is a chromophorous pigment bacterium, whose 
pigment only forms at growth in the light. 
5th B. stutzeri and B. vulpinus behave towards free oxygen like 
aerobic spirilla, B. denitrojluorescens behaves like an ordinary aerobic 
bacterium. 
Gh. Like in soil and dung, in which it had also been found by 
other experimentators, | have established the general distribution of 
denitrifying bacteria in canal and sewage water. 
7h. The denitrifying bacteria can, even with the slightest quantities 
of various organic substances, cause the disappearance of determined 
quantities of nitrate under development of free nitrogen. 
Sth. In one and the same culture medium, where nitrification is 
produced during aeration, denitrification may be caused by exclusion 
of air, this holds good also in regard to the soil. 
At the end of this paper I want to express my sincere thanks to 
Professor Dr. M. W. BrijerincK for his kind, invaluable guidance 
and efficacious assistance, afforded me in these researches. 
Delft, July 1902. 
Physics. “An Hypothesis on the Nature of Solar Prominences.” 
By Prof. W. H. Joxivs. 
The introduction of the principle of anomalous dispersion into 
solar physics makes it possible to form an idea of the Sun’s consti- 
tution from which necessarily follow ia. a great many peculiarities 
of prominences, which, until now, it has been impossible to deduct 
in a satisfactory manner from other physical laws. This I will 
show in the following pages. 
In my paper on “Solar Phenomena, etc.” read Febr. 24, 1900. 
I put forth the following hypothesis with respect to that part of the 
solar atmosphere, situated outside what is called the photosphere *): 
1) W. H. Junius, Solar Phenomena, considered in connection with Anomalous 
Dispersion of Light, Proc. Roy. Acad. Amsterdam, Il, p. 585. 
