ISO On the Porcelain Earth of Comwall. [AfARCH, 



T!ie cn'stallized oxalic acid consists of 1 atom of acid and 2 of 

 water. The proportions are as under : — 



Per Theory. Thomson. Berard. Berzelius. 



Real oxalic acid.. 71-4 77 727 71-25 



Water 2S-6 J3 273 28-75 



100 100 100 100 



It is remarkable that Berzelius determines the water in the 

 ervstals of oxalic acid, as it should seem, with great accuracy ; but 

 that when the acid is combined with lead it loses (according: to him) 

 about 14 per cent, more of water. Now this does not happen ia 

 the case of the other insoluble oxalates, such as that of lime ; for 

 Dr. Thomson found 77 parts out of 100 of crystallized oxalic acid 

 to exist in the dry oxalate of lime obtiiiaed from it. This circum- 

 stance is of itself sufficient to render Berzelius' analysis of the 

 oxalate of lead doubtful. Querj' : What temperature was his 

 o.xalate of lead dried in ? 



Wxih resp>ect to the theory of volumes, to which Berzelius seems 

 inclined to give the preference rather than to that of atoms, it is not 

 my intention to say much at present. I shall wait to see it more 

 fully developed. I own 1 do not see how we are to remove the 

 difficulties attending the atomic theory by substituting the term 

 voluyne for that of atom ; nor how " we can figure to ourselves a 

 demi-vohme, while in the theory of atoms a detnl-atovi is an 

 absurdity." Notwithstanding this, whatever may come from the 

 pen of Berzelius on the subject will, no doubt, be worthy thr 

 attention of the chemical world. 



Article IV. 



On the Porcelain Earth of Cormi-all. By William Fitton, MD. 



of Northampton. 



(To Dr. Thomson.) 

 DEAR SIR, 

 The enclosed paper was drawn up a few years ago, at the desire 

 of some friends, from notes which 1 Ijad taken in Cornwall : it has 

 not been in my power to render it complete ; but if you think it 

 worth inserting ia your Journal, it is at your service. 



I am. Dear, Sir, &c. &c. 

 Aw. 1813. William Fitton. 



Tlie principal earthy substances obtained in Cornwall, that are 

 used in the manufacture of the finer kinds of earthenware, are : 



