52 MINERALOGICAL NOTICES. 



Iron Lode, I found the specimen of Blue Phosphate of Iron which 

 I now present to the Royal Institution. I have also found 

 Phosphate of Lead on several occasions — always, however, near 

 some of the numerous intersections of the lode by lead lodes. 

 The occasional occurence of these minerals may, perhaps, explain 

 the extraordinary analyses of the Perran Iron Ores which have, 

 from time to time, been published. I have had occasion recently 

 to examine scores of samples, specially for Phosphoric Acid. In 

 some instances I have found none — sometimes only a trace — at 

 others, quantities of Phosphoric Acid varying from -1 p. c up to 

 2 -4 5 p.c,* which is the highest I have ever been able to find. 

 One analysis, however, giving 6-99 p.c of Phosphoric Acid is on 

 record, and if the portion analysed contained a fragment of either 

 of these phosphates, such a result might be expected. These 

 facts illustrate the importance of Mineralogical knowledge, not 

 only to the workman who picks over piles of iron-ore for the 

 market, but also to the chemist who analyses the sample. 



* A later analysis of ore from near a cross-course at Gravel Hill gives 

 3'84 p.c of Phosphoric Acid. 



