Chem 1st ry and P/> y* u **. 1 1 r> 



i> also at times crossed bj another at right angles to it, that 

 is, inclined about 4.V to the basal edge in the opposite direc- 

 tion- Those points merit a closer study than it has been possi- 

 ble to give them thus far. Thev remind one of the twinning 

 lamella- parallel to the maerodomo 601 described by Bauer,* 

 but thev do not seem here to be connected with any variation 

 of optical orientation. 



In conclusion, the writer regards it as proved beyond doubt 

 for the specimens which he has had in hand from Perkins' 

 Mill, that thev are normal barite ; and that the existence of a 

 monoclinic form of barium sulphate among specimens from 

 that locality is extremely doubtful. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Decomposition of Carbon disulphide by Shock. — 

 On attempting to reduce liquid carbon disulphide by means of a 

 liquid alloy of potassium and sodium, Thorpe obtained a yellow- 

 ish-brown powder encrusting the alloy, which exploded violently 

 when the bottle was shaken ; this powder being found subse- 

 quently to detonate with more violence than diamine di-iodide. 

 The hand of the operator was coated with a black deposit, con- 

 sisting apparently of finely divided carbon. Reflection con- 

 vinced the author that this deposit was far larger than could have 

 come from the decomposition of the brown powder itself, and as 

 carbon disulphide is an endothermic compound, absorbing in its 

 formation according to Thomson 19610 calories, it appeared not 

 at all improbable that, like acetylene, cyanogen, nitric and nitrous 

 oxides, the oxides of chlorine, etc., it might experience decompo- 

 sition by a sudden shock ; and that in the above case, the carbon 

 disulphide had been resolved into its elements by the violent 

 explosion of the yellowish brown powder. Actual trial showed 

 that mercuric fulminate would produce the same effect ; and 

 Thorpe suggests the experiment as an easy and safe method of 

 showing in the classroom the decomposition of an endothermic 

 compound by shock. For this purpose a thick glass tube about 

 600 aim long and 15 mm wide is fitted at one end with a rubber 

 stopper carrying two stout wires, on the lower end of one of 

 which is a small cup, like a deflagrating spoon, while the other 

 wire is bent so as to come within 'i or 3"" n of the bottom of the 

 cup. In this cup is placed about 0*05 gram of mercuric fulminate. 

 A piece of paper slightly longer than the tube is moistened with 

 carbon disulphide and placed within the tube and the cork is put 

 in. After a minute or so, the tube being inclined at 45°, the 

 vapor of the disulphide will practically fill it and the paper may 



* Jahrb. Min., i, 37, 1887. 



Am. Jour. Sci.— Third Series, Vol. XXXIX, No. 229.— Jan., 1890. 

 5 



