of Edinburgh, Session 1880-81. 
293 
shire boulders have come; whilst the fact, if it he verified, that 
they did come across the Atlantic from the west, is an additional 
link in the circumstantial chain which supports a theory advocated 
by the distinguished naturalists to whom I have referred. 
The inquiry, however, being of considerable geological interest, I 
should wish that the positions of the boulders on the west coast of 
Scotland did not rest on my personal observation (as at present 
they chiefly do), but that they would engage the attention of others, 
and who, I hope, will report the result of their enquiries to the 
Boulder Committee. 
2. On the Compression of Gases by High Pressures. 
By Professor Tait. 
3. Determination of Longitude without a Chronometer. 
By Dr Menzies. Communicated by Professor Tait. 
4. The Electric Discharge through Colza Oil. 
By A. Macfarlane, M.A., D.Sc., F.B.S.E. 
(Abstract.) 
The dielectric strength of colza oil (specific gravity *91) was found 
to be 2*7, that of air at the ordinary pressure being unity- The 
rest of the paper is taken up with a description of the phenomena 
accompanying under different conditions the spark discharge through 
the oil. 
5. On Quaternion Integration. By Professor Tait. 
The Chairman closed the session with the following 
remarks : — 
I have now, in a very few words, to close this session, and in so 
doing I beg to remind you that it is the ninety-ninth session of the 
Poyal Society of Edinburgh. This Society, which was originally an 
offshoot of the University of Edinburgh, was first started, on the 
suggestion of Principal Kobertson, towards the close of 1782. So 
that in the latter part of next year you will be able to announce 
your hundredth birthday. The Society came into existence just 
one year after its late distinguished President, Sir David Brewster, 
