( 292 ) 



e.g. in the case of a Michelson echelon spectroscope, if the incident 

 light lias been previously analyzed by means of an auxiliary 

 spectroscope. Reflection and refraction in the glass prisms of course 

 weakens to different amounts vertical and horizontal vibrations. 



Cases in which relation (1) fails are to be observed in some 

 spectra with many lines (e.g. iron). Among adjacent magnetic triplets 

 some are to be detected in which the distribution of intensity in 

 one resembles figure J, in the other figure 2. Without further 

 analysis one may conclude that for the one or for the other relation 

 (1) fails. 



EXPLANATION OF THE PLATE. 



The figures are thirtyfold enlargements of negatives concerning the mercury line 

 5769, 4. 



In all cases the image of the source was projected on the slit with a glass lens. 



Fig. 1. No quartz plate in front of slit. 



Fig. 2. Quartz plate, rotating plane of polarization 45° in front of slit. The 

 distribution of light corresponds to that in source. 



Fig. 3. Quartz plate, rotating plane of polarization 90° in front of slit. Though 

 the time of exposition was thrice that used with the other figures, there appear 

 only traces of the outer components in the original negatives. 



Chemistry. — "On lupeol." By Prof. P. van Romburgh. 



In the Comptes rendus of June 24, 1907, Jungfleisch and Leroux 

 state that lupeol cinnamate occurs in the gutta percha of Palaquium 

 Treubii Buck. 



I have demonstrated previously that cinnamic acid may be obtained 

 from this species of gutta, whereas lupeol cinnamate proved to be a 

 constituent of different commercial varieties of gutta percha '). 



Jungfleisch and Leroux have now studied the lupeol obtained by them 

 and state that this substance on heating suddenly on the "bloc Maquenne" 

 melts at J 90° — 192°, then immediately solidifies and mells again at 

 212°. They explain this phenomenon by assuming that lupeol loses 

 water and is converted into a hydrocarbon, melting at 212°, to which 

 they give the name of lupeylene. At ISO 1 lupeol would lose water 

 slowly, very rapidly so at 150 1 — 160° and suddenly at 190". 



') B.B. 37 (1904) 3442. 

 •i Hiss. Utrecht 1906. 



