26 REPORT — 1839. 



The limestone pitched upon for this experiment was that 

 called the Five Yards Limestone, and the sandstone the Six 

 Fathoms Hazle, the plate bed between them being three feet in 

 thickness and a little more strongly indurated than the plate 

 beds in the district usually are. There was a flooring or hunyan 

 across the shaft at this place, and a level or drift driven out of 

 the shaft to a small distance, in which the galvanometer was 

 placed. The situation was at a distance from any vein, and all 

 the circumstances were of the most favourable nature for per- 

 forming the experiment with the utmost completeness and pre- 

 cision. 



Six holes, each two feet deep, were bored in the sandstone a 

 foot above its under surface, and six similar holes were bored in 

 the limestone a foot below its upper surface ; into these holes 

 were introduced twelve slips of sheet copper, each two feet long 

 by two inches wide, bent so as to be semi-cylindrical, and they 

 were fixed and stemmed very tightly into the holes so as to se- 

 cure the most perfect contact. The six copper slips in the hazle 

 were connected with a copper wire one twentieth of an inch in 

 diameter, the end of which, as before, was attached to one pole 

 of the galvanometer, and the six coppers in the limestone were 

 similarly connected together and brought in contact with the 

 other pole of the galvanometer. Every possible care was taken 

 in attaching the wires and in making the contacts, but the needle 

 of the galvanometer did not show the slightest current, although 

 at the same time it was fully sensible to the action of the plates 

 of zinc and copper, one eighth of an inch square, in pure water. 

 When the contacts were made at intervals so as to be isochro- 

 nous with the times of vibration of the needle, and continued for 

 several minutes, there was still no appreciable effect whatever. 



It was thus fully established that under the circumstances 

 detailed, there was no current given off equal in amount to that 

 excited by a pair of plates of zinc and copper, one eighth of 

 an inch square, in pure water ; indeed, when we reflect upon the 

 thickness and imperfectly conducting nature of the strata, no 

 very obvious current could be expected. It is, however, still 

 possible that, by using a more delicate galvanometer, bringing 

 into contact with each stratum a larger surface of metal, and 

 including a greater number of alternations of strata within the 

 circuit, a current may yet be detected, and the matter is certainly 

 open for further investigation. 



Bensham Grove, Gateshead. August 24th, 1839. 



