194 Proceedings of the Royal Society of Edmhurgh. 
Humboldt, and, by giving a position to the two poles, and as- 
suming their temperature, he deduced a general formula for all 
meridians, and shewed, that the difference between the calcula- 
ted and observed results were far within the limits of the errors 
of observations. The form of the isothermal lines resembles gene- 
rally that of the isochromatic curves which surround the resultant 
axes of crystals with two axes of double refraction. In conclu- 
ding this paper, the author pointed out the analogy between the 
magnetic and the isothermal curves in the polar regions : he no- 
ticed their similarity of position, and, conjecturing that these 
isothermal poles might have a motion of revolution round the 
pole of the earth, he shewed how, upon such a supposition, the 
low temperature of ancient Europe might be explained, and 
how we might account for the remains of plants, and land and 
sea animals being found in climates where they could not now 
exist. / 
At the same meeting, an account of the Journey of Alexan- 
der Scott, through Africa, drawn up by Dr Traill, was read. 
See this Number, p. 38. 
Alexander Irving, Esq. communicated an extract of a letter 
which he had received, giving an account of the Earthquake 
which was recently felt at Leadhills. See p. 215. 
Art. XXXIV. — Proceedings of the Wernerian Natural His- 
tory Society. 
Aug. 5. 1820. M. Greville read a paper, containing an 
account of some of the Cryptogamous Plants of Devonshire, 
and communicating some new facts relative to several species 
of Fucus, particularly one discovered by Mrs Griffiths, so well 
known by her botanical researches. She had long observed, 
that when Fucus laciniatus occurred without the marginal 
processes, in which the seed-bearing tubercles are contained, 
the margin was of a darker colour than the rest of the frond : 
this, on a careful examination, proved to be formed by ex- 
tremely minute single seeds. Mr Greville has since confirm- 
ed Mrs Griffiths’s observation; and Fucus laciniatus must, 
therefore, be added to those which have two modes of fruc- 
