Mr. Smith's Maps of the Strata. 333 



flask of glass with a neck many inches long was half-filled with 

 mercuiy, and coated on the outside to the same height with foil. 

 By means of a moveable wire, an electric charge was thrown in ; 

 the wire was drawn out, and the neck was hermeiically sealed. 

 After a length of time the sealing of the neck was cut offj the 

 wire was plunged into the mercury, but not the smallest com- 

 inotion was perceived by the hand j althougli the original charge 

 was capable of giving a violent shock. Thus I had encompassed 

 a quantity of electricity on all sides by glass: after a certain time 

 I found that the glass contained none. What should I conclude, 

 but that it escaped ? Were Mr. De Luc to repeat this experi- 

 ment, he would certainly consider my inference as natural." 



I am too old and too infirm to undertake any new experi- 

 ments ; I shall therefore only suggest an idea which Mr. Do- 

 novan may easily try. Glass becomes a conductor when healed^ 

 thus it may be that the /lask was discharged, by the operation 

 of sealing it; for the operation of hermetically sealing it, re- 

 quires a great heat. I therefore suspect that the moment when 

 the flask was sealed, it was discharged. This appears to me 

 more natural than to suppose, against all the known phaenomena 

 of the Leyden vial, that glass is permeable to the electric mat- 

 ter. But Mr.Dono\an might easily put it to the test of experi- 

 ment in the manner above pointed out. 

 1 am, sir, 



Your most obedent servant, 



J. A. Dfc Luc. 



LXJ. Olservations on the Priority of Mr. Smith's Investiga- 

 tions of the Strata of England ; on the very unhandsome 

 Cofidiict of certai}i Persons in detracting from his Merit 

 therein ; and the Endeavours of others to supplant him in the 

 Sale of his Maps; — with a Reply to Mr. W. H. Gilby's 

 Letter in the last Number. By Mr. John Farey, Sen. 



To Mr. Tilloch. 



Sir, — XHE rash and unfounded reflections, which a Mr. 

 IV. H. Gilby has been induced to address to you from Edin- 

 burgh, pages 'SO') and 301 of your last Number, would not at this 

 lime iiave occasioned me to trouble you thereon, but for the very 

 euper'or calls oi justie as well as friendship, in favour of Mr. 

 fVil'inm Smith's irresistible claim to the discovery of the order, 

 and tri j)riority in the actual tracing and mapping of the surfaces 

 of the principal part q{ the British series of Strata, ^nd those 

 scarcely less urgent calls, to support the cause of practical Eng- 

 lish 



