4-80 Queries and Answers. 



Having brought together these variable statements, I must 

 leave them to be reconciled by some one who has more leisure 

 than myself. The foreign measures named (in No. 114.) are 

 the German mile, which is equal to 4 and a fraction English 

 miles; the league of the value of 25 to a degree; the toise 

 =r 6*395 English feet; and the metre zz 39*371 English inches. 



It may be that the action of volcanoes and earthquakes, not 

 uncommon in the Caspian and its vicinity, occasionally and 

 partially alters, from time to time, the depth, extent, and level 

 of that and the mtf[&&mt^ve&s 'ip&r-bye&s Geology, vol. i. 

 p. 320. &c. ; and Dr. Daubeny, On Volcanoes, p. 300.); but 

 the above statements require some other correction. — W. B. 

 Clarice. Parkstone, May 23. 18W. r ~'~ 



An Ore which acquires a white Incrustation. — I have in 

 my cabinet a specimen of iron which exhibits a phenomenon, 

 with the cause and nature of which I am quite unacquainted. 

 I have no doubt that it is iron ; since, when to a solution of 

 the ore I had applied a solution of prussiate of potash, the 

 liquid was instantaneously coloured blue. Specimens of this 

 ore, when kept for some time undisturbed, on being opened 

 out were covered with a white incrustation, having the appear- 

 ance of minute crystals. Can any of your readers account 

 for this circumstance ? — J. E. L. Richmond, Yorkshire, 

 August 4. 1832. 



It is impossible to say, from the above description, what 

 ore of iron is alluded to ; nor is the phrase " opening out" 

 properly explained. Most likely <( the specimen" is a mass 

 of radiated or of hepatic pyrites (sulphuret of iron), very 

 common, in the radiated form, in some beds of the chalk 

 formation, as at Cherryhinton, near Cambridge, Godstone, 

 Surrey, &c. When exposed to the air, the oxygen unites 

 with the sulphur ; and a white silky efflorescence, or " minute 

 crystals," result from the decomposition. A coating of varnish 

 will preserve the specimens, and prevent " the disease," as it 

 has been called, spreading to other minerals in the cabinet ; a 

 precaution sometimes not altogether unnecessary. In the 

 London clay, on the Suffolk coast, there are immense quan- 

 tities of pyritous wood : from the decomposition of which, at 

 Walton in Essex, great quantities of copperas used to be 

 manufactured. In the gault at the brick kilns, near the Ely 

 entrance to Cambridge, I have seen the pyritous balls, which 

 abound there, partially decomposed ; presenting, in the same 

 mass, crystals of selenite, which have resulted, as in the 

 Oxford clay at Shotover Hill, from the pyrites. — W. B. C. 

 Parkstone, May 31. 1833. 



