Reports and Proceedings. 75 
established as a fact, it would throw a flood of light on a very obscure 
question. 
The Rev. Dr. Haucuton said he had omitted to state that the 
geology of the Islands in question derived an additional interest from 
the observations of General Sabine, to which the Chairman had just 
alluded, as to the magnetic properties of the rocks. The labradorite- 
and. augite- rock of Skye contained a large quantity of magnetic 
iron, of a high specific gravity, as he had mentioned, resembling the 
syenite of Donegal. Colonel Sir Henry James, who had been 
engaged in investigations for the purpose of comparing the mea- 
sured are of the meridian in England with ares measured in France, 
Prussia, Russia, and Italy, told him that, on approaching Aberdeen, 
a deviation of the plumb-line occurred, which he was quite unable 
to explain. He showed him a specimen similar to the rock now on 
the table, which contained a large quantity of magnetic iron, and 
stated that he believed it extended in a broad band through the 
North of Scotland. It had a specific gravity which was very high, 
and capable of influencing both the magnet and the pendulum. 
There were no questions of greater interest in connection with the 
theory of the earth than those which were opened up and explored 
by such investigations conducted for the purpose of measuring the 
ares of the meridian. Professors Maskelyne, Hutton, and Playfair 
had been completely baffled in their investigations in connection 
with the Mountain Schiehallion. He believed the cause to be 
that they had omitted to take into account rocks of exceptional 
density, and had in consequence estimated the density of the moun- 
tain too low, and accordingly derived too low a density for the earth. 
There was reason to think that rocks of the character just alluded 
to ran through Schiehallion. Corrections by modern physicists of 
their observations went to show, that if they had known what the 
real weight of Schiehallion was, they would have got at the real 
specific gravity of the earth. From observations which he himself 
made at Loch Scavig with a pocket-compass, and also with the 
compass of the yacht, he was perfectly satisfied that that mountain 
was what an ancient mariner would have called a loadstone, which 
was due to the large quantity of magnetic or titanic iron in it. 
The Cuarrman observed that General Sabine, Professor Phillips, 
and himself, while engaged in the magnetic survey of the kingdom, 
made observations and calculations which, when collated, went to 
show that the magnetic disturbance in England—in which country 
sedimentary rocks are the most prevalent—was least; that in Ireland 
was next; and that in Scotland it was the highest of all. 
Mr. Ormssy then made a communication respecting the Island of 
Ezgg, of which the following is an abstract :—He remarked that on 
a recent yachting-visit to the district just described by Prof. 
Haughton, he had been enabled to confirm his observations as to the 
Islands being composed of Secondary or Tertiary rocks, capped by 
basalt. This is to be seen in a very remarkable way in the small 
Island of Eigg, lying between Mull and Skye. The base of the 
