284 MAGNETIC ROCKS OF CORNWALL. 



The average affinity of each sample of rock after 12 mouths 

 repose was very similar. 



The bar magnet employed was 1 foot long, IJ inch wide, 

 and i inch thick. 



A slice of rock with an affinity of 5^ grs.. was sufficient to 

 hold this bar magnet at right angles, either east or west of the 

 magnetic poles of the earth. 



