10 



Prehistoric age — the Neolithic of the cave — is so great and 

 so full of difficulty that it cannot be gauged by any method 

 which has hitherto been invented. 



Mr. Boyd Dawkins also exhibited a remarkably perfect 

 javelin head of bronze which had been dug up in a field 

 near Settle. 



"Note on the Chromium Oxychloride described by Hr. 

 Zettnow in Poggendorff 's Annalen der Physik und Chemie, 

 No. 6, 1871/' by T. E. Thorpe, F.RS.E. 



In the above-mentioned number of Poggendorff 's Annalen* 

 Hr. Emil Zettnow describes an oxychloride of Chromium to 

 which he assigns the formula CrgCl^O -f 4Cr03. It is obtained 

 by treating potassium chloro-chromate (K2Cr2O60l2) with 

 strong sulphuric acid, and, after a somewhat tedious course 

 of preparation, appears as a brownish black, brittle, amor- 

 phous substance, exceedingly hygroscopic, and giving up its 

 chlorine with great ease. Hr. Zettnow's analytical results 

 and the numbers required by his formula are : — 



Found. Calculated. 



Cr 47-28 47-23 



CI 22-31 21-42 



— 31-35 



100.00 

 In the Proceedings of the Literary and Philosophical 

 Society of Manchester for Nov. 2nd, ISGD,"!* I described a 

 solid chromium oxychloride obtained by simply heating 

 chromyl dichloride in a sealed tube, and which, on com- 

 pletely freeing it from the latter body, " appears as a black 

 non-crystalline powder, which, when exposed to the air, 

 rapidly deliquesces to a dark reddish brown syrupy liquid, 

 which smells of free chlorine" (loc. cit.) These properties, it 

 will be observed, are precisely those which Hr. Zettnow 

 describes as belonging to his chromate of chrom-oxy chloride. 



* See also " Cliem. News," Sept. I5tli, 1871. 

 t Also " Chem. News," Nov. 19th, 1869. Zeitschrift fur Chemie, 



Jan., 1870. 95. 



