Intelligence and Miscellaneous Articles. 319 



the magnetic molecular force, which accords well with experiment. 

 — Sitzung der math.-naturw. Classe d. kaiserl. Akad. d. Wissensch. 

 in Wien, February 12, 1874. 



ON A PECULIAR OCCURRENCE OF CRYSTALLIZED SILICIC ACID. 

 BY THEODOR HUBENER, OF ROSTOCK. 



About a year since, I was treating some Grblitz browncoal for the 

 purpose of exhibiting microscopic products with Schultze's macera- 

 tion-fluid (a solution of chlorate of potass in nitric acid). After 

 the coal had been sufficiently treated with the liquid, and then 

 extracted with ammonia and alcohol, the microscopic examination 

 showed in the residue a quantity of minute crystals the form of 

 which (six-sided columns pointed at both) ends) left no doubt that 

 they consisted of crystallized quartz. By repeated ignition of 

 the residue and treatment with hydrochloric acid, they could 

 be readily isolated. From, at the most, 1 kilogramme of the 

 coal, I have in this way obtained about 3 grammes of the crystals. 

 I have not at present found them in other browncoals. Unfortu- 

 nately I have not yet succeeded in obtaining some of the sand which , 

 perhaps overlies the browncoal ; but as the residue above mentioned 

 contains scarcely any grains of ordinary quartz, it might be supposed 

 that, by the influence of the products occurring in the gummif action 

 of coal (humic acid &c), solution of siliceous salts infiltrated into 

 it may be decomposed, whereupon the silicic acid is separated as 

 crystals. My attempts (only on a small scale, it is true) to separate 

 silicic acid in crystals by protracted digestion of humous substances 

 with solutions of siliceous salts have been without result. I shall, 

 however, continue these experiments during a longer time ; and I 

 have no doubt .that in this way I shall succeed in separating crys- 

 tallized silicic acid from solutions. — Poggendorff 's Anncden, vol. cl. 

 p. 643. 



ON THE SPECTRUM OF THE LIGHT OF EXPLODING GUN-COTTON. 

 BY O. LOHSE. 



The yellowish flame produced when pyroxyline is ignited gives 

 a very interesting spectrum. I first observed it, with a Browning 

 miniature spectroscope, in January 1872, at a time when the fre- 

 quently occurring phenomena of the aurora borealis induced me to 

 investigate the origin of its spectrum. I thought then, on super- 

 ficial consideration, that I could recognize a certain similarity be- 

 tween the latter and the spectrum of exploding gun-cotton — a 

 sufficient reason for undertaking, in conjunction with Dr. Vogel, an 

 accurate examination of this spectrum with a larger spectrum-appa- 

 ratus which permitted the measurement of the lines and the deter- 

 mination of their wave-lengths. The result was that the lines of 

 the two spectra did not coincide. 



If I take leave to communicate in the following the details of the 

 investigation, it is in view of the interesting experiments which 

 have taken place in the Arsenal at W oolwich, on the velocity of pro- 

 pagation of the explosion of pyroxyline. 



