( 789 ) 



With the osciHations of long duration that inaccuracy in the 

 registration does of course not appear. 



So we come to the conclusion that the oscillations of short and 

 of lorn/ duration of the magnetic force at Batavia and at Buitenzorg 

 have the same ratio of amplitude and that they therefore cannot be 

 caused, or only for a small part, by the current running through 

 the outer crust of the earth. 



By far the greater part of the influence of tlie earth-currents 

 must therefore come from currents at greater depths and of greater 

 extensioi>, and more equal in intensity. 



Chemistry. — "On the 2^ri-para-Halogen-Substitution-Products 

 of Triphenyhnethane and Triphenylcarbinol." By Dr. F. M. 

 Jaeger. (Communicated by Prof. A. P. N. Franchimont). 



(Communicated in the meeting of March 28, 1908). 



§ J. Some years ago, I investigated^) crystals of Tri-p-Chloro- 

 Triplienylmethane, from different preparations which had been obtained 

 by Dr. P. J. Montagne in two different ways, namely from p-leuca- 

 niline by diazotation and subsequent introduction of the three chlorine 

 atoms and from fetrachlorobenzopinacoline by intramolecular rearran- 

 gement. 



1 then gave a detailed description of the remarkable optical be- 

 haviour of the compound in convergent polarised light and endeavoured 

 to elucidate the same by a coloured figure. 



Wishing to extend this research also to tiie other halogen-deriva- 

 tives, I have first of all prepared the tribromoderivative of ;:*-leu- 

 caniline by the method proposed by 0. Fischer and W. 

 Hess. -) Afterwards I received from Prof. F'ischer a small quantity 

 of each of the three halogen derivatives, which enabled me to prepare 

 the three corresponding trihalogen-carbinols by oxj'dation with chromic 

 acid in acetic acid solution, so that these three substances could be 

 included also in this investigation. I will not omit to thank this savant 

 once more for his kind assistance. 



Of Tri-p-Brornotriphenylmethane ^) I gave a description a short 

 time ago in the Zeits. f. Kryst. 44, 57—58. (1907). The habit of 

 the crystals is quite analogous to that of the chloro-compound ; they 

 are more compact of form and generally much larger, but at the 

 same time they cannot be measured so accurately, owing to a curving 



^) Receuil 24. 124, 131. (1905). 



2) 0. Fischer und W. Hess, Berl. Ber. 38. 336. (1905). 



3) F. M. Jaeger, Zeits. f. Kryst. und Miner. Bd. 44. 57. (1907). 



