( 348 ) 
a solution of the substance which decomposes the indican. The dried 
leaves of Indigofera galegoïdes, as also some other kinds of leaves 
with which experiments were made, were incapable of producing the 
decomposition, so that it appears to be a specific property of some 
indigo yielding plants. These researches, which proceed slowly, will 
be continued, as also those on the substance which on oxidation 
gives rise to indigo; this substance may also be extracted by carbon 
tetrachloride.” 
Finally in the recent “Verslag” for 1898: 
“Investigations on the composition and properties of a red com- 
pound, which is obtained by evaporation of the chloroform soiution of 
the liquid decompositionproduct of indican from Indigoferas which 
yields indigo, progress but little owing to lack of time. MARCHLEWSKI 
and RapcLirFE (Chem. Centralbl. 1898, II, 204), consider indican 
to be the glucoside of indoxyi. The properties of the decomposition 
product which yields indigo on oxidation, and which has already 
been shown here not to be identical with indigowhite, agree, to some 
extent, well with those of indoxyl. Since Mr. HAZEWINKEL, Director 
of the Experimental Station at Klaten is occupied with this matter, 
I have not followed it further.” 
Physics. — Dr. E. van EVERDINGEN JR.: “The Harr-effect and 
the increase of resistance of bismuth in the magnetic field at very 
low temperatures” 1 (continued). (Communication N°. 53 (cont.) 
from the Physical Laboratory at Leiden, by Prof. H. KAMER- 
LINGH ONNES.) 
5. In the Proceedings of October 28, 1899, p. 221, I expressed the 
hope that the measurement of the Harrr-effect at the boiling-point 
of liquid oxygen would yield a more decisive answer to the question 
as to whether or no this phenomenon has a maximum at low tem- 
peratures. This measurement has now been made, though as yet 
only for one strength of field, and the answer is certainly a decided 
negative, as will appear frem § 7. 
6. The liquid oxygen bath. For pouring out the liquid oxygen 
we used the vessel without a vacuum-wall, described and drawn in 
§ 2 of this communication, but somewhat altered for this purpose 
after the manner of Prof. KAMERLINGH ONNES’ cryostat !). Besides 
1) See Communication N°. 51, Proc. 30 Sept. °99. p. 126. Comm. Phys. Lab. 
Leiden N°. 51, p. 2. 
