MR. A. W. RUCKER AND DR. T. E. THORPE OX A MAOXETIC 
27 r, 
Eig. 12. 
The Island of Canna. 
The attraction exerted by the Malverns having been demonstrated, it is convenient 
to discuss in the next place a locality where the disturbances are enormously greater. 
Popular tradition has long attributed to the basaltic rocks of the Island of Canna 
the power of deviating the needle through very large angles. The compasses of 
passing ships are supposed to be affected by the eastern extremity of the island, on 
which stands Compass Hill. 
Magnetic observations were made on the Island by Sir Frederick Evans (‘ Phil. 
Trans.,’ 1S72, vol. 1G2, p. 825), but, we have, we believe, been able to add con¬ 
siderably to what was already known of its magnetic properties. 
The island, which is about fifteen miles south-west of Skye, is about five miles long, 
its greatest length lying nearly due east and west. It is divided into two approxi¬ 
mately equal portions by a neck of comparatively low elevation. The highest ground 
is in the eastern part where it rises to a height of 724 feet, and our observations have 
been confined to tliis portion. The cliffs on the north side are here some hundreds of 
feet in height and fall sheer into the sea. On the south side several small valleys 
lead to the shore, but the hills rise very steeply about a quarter of a mile inland, and 
the tops of several consist of irregular masses of basaltic columns. On Compass Hill, 
