Chemical Observations. 359 



The dichromate of lead is itself of a full red colour, and is 

 best prepared according to the original process of Mr. Badam's 

 (Annals of Philosophy, N. S. vol. ix.), by digesting a solution 

 of the yellow chromate of potash upon carbonate of lead at a 

 boiling temperature, in the proportion of one atom of the 

 former to two atoms of the latter, stirring up the solid matter 

 very frequently, as the action is far from energetic. 



Caustic potash likewise converts the chromate of lead into 

 the dichromate; but, from its strong disposition to dissolve the 

 oxide of lead, as well as to withdraw chromic acid, did not 

 answer with us for forming the dichromate. 



It occurred to Mr. R. Ruathen, while engaged with this 

 subject in my laboratory, to try if the dichromate would stand 

 the glazing heat of a potter's kiln, which it was found to do, 

 and to form a pretty good red on ordinary kinds of stone- 

 ware. 



Geological Survey of the Island of Jersey, By Lieutenant 

 Nelson, Royal Engineers, Corresponding Member of the 

 Plymouth Institution.* 



Thb Jersey rocks may be referred to three classes, that of the 

 argillaceous schists, that of such as are distinguished by the 

 presence of felspar, and lastly, that of the breccia, composed 

 of both. 



The felspar rocks overlay the breccia and argillaceous 

 schist, alternating with the last, which is also overlaid by the 



breccia. 



Argillaceous Schist. 



Beginning at L'Etac in St. Ouen's bay, a remarkable junc- 

 tion is observable in the little bay «, where the sienite joins 

 the schist, and penetrates it in large irregular veins. About a 

 mile to the south is the mouth of a remarkable valley, at the 

 bottom of which, for nearly its whole length, lies the line of 

 separation between argillaceous schist and the sienite, which 

 last is obviously incumbent : a small portion of the former 



* The letters in this paper refer to a map, which we have not been 

 able to prepare for insertion in this Number. 



