156 Intelligence and Miscellaneous Articles. 



This reappearance of a previous polarization I have already en- 

 deavoured to account for by the depolarizing current only removing 

 the gases from the most superficial layer of the platinum, new 

 supplies of gas pressing afterwards from the deeper parts to the 

 surface. This takes place, therefore, in the same manner when 

 the entire store of gas is derived from the other side. 



Experiments made by Dr. Hoot, with a suitably modified appa- 

 ratus, on the question whether free hydrogen in contact with the 

 off side of B, while free oxygen was on the off side of C, would 

 penetrate through the plates and produce polarization on the other 

 side, did not give sufficiently explicit results. In these cases even 

 the electrical force is wauting which urges the positive hydrogen 

 molecules into the platinum. — MonatsbeHcht der honiglich preu- 

 ssischen Akademie der Wissenschaften zu Berlin, March 1876, pp. 

 217-220. 



ON ROSCOELITE A VANADIUM MICA. BY F. A. GENTH. 



I am indebted to Dr. James Blake, of San Francisco, California, 

 for a small quantity of the very interesting mineral which he called 

 "Roscoelite" in honour of ProfessorEoscoe, whose important investi- 

 gations have put vanadium in its proper place among the elements. 



Roscoelite occurs in small seams, varying in thickness from -£$ to 

 T \)- of an inch, in a decomposed yellowish, brownish, or greenish rock. 

 These seams are made up of small micaceous scales, sometimes 5 of 

 an inch in length, mostly smaller, and frequently arranged in stel- 

 late or fan-shaped groups. They show an eminent basal cleavage. 

 Soft. The specific gravity of the purest scales (showing less than 

 one per cent, of impurities) was found to be 2-938 ; another speci- 

 men of less purity gave 2-921. Lustre pearly, inclining to subme- 

 tallic. Colour dark clove-brown to greenish brown, sometimes dark 

 brownish green. 



Before the blowpipe it fuses easily to a black glass, colouring 

 the flame slightly pink. With salt of phosphorus gives a skeleton 

 of silicic acid, a dark yellow bead in the oxidizing flame, and an 

 emerald-green bead in the reducing flame. Only slightly acted 

 upon by acids, even by boiling concentrated sulphuric acid ; but 

 readily decomposed by dilute sulphuric acid when hervted in a 

 sealed tube at a temperature of about 180° C, leaving the silicic 

 acid in the form of white pearly scales, and yielding a deep bluish- 

 green solution. With sodic carbonate it fuses to a white mass. 

 The Boscoelite which I received for investigation was so much 

 mixed with other substances, such as gold, quartz, a feldspathic 

 mineral, a dark mineral and very minute quantities of one of orange 

 colour, tbat it was impossible to select for analysis material of per- 

 fect purity. For this reason I have delayed the publication of my 

 results, which were obtained over one year ago, in the hope of 

 being able to repeat my analyses with better and purer specimens ; 

 but 1 now give the results of my analyses because there is no pros- 

 pect of getting any more of this mineral, as in a letter of Dr. 

 Blake, dated j?an Francisco, April 5th, 1876, he says that the mine 



