PHOCEEDINGS OF GEOLOGICAL SOCIETIES. 
263 
The intimate relationsliip traceable between the Tertiary and Japanese 
floras in the numerous characteristic t3-pes common to both ; the issue of 
the ordinal and generic comparisons given above ; the larger proportion 
of ligneous species in the Japanese than in the Eastern American flora ; 
and the number of types peculiar, at the present day, to Eastern America 
and Eastern Asia, compared with the few restricted to Europe and 
America, the speaker contends, favour the view advanced by Professor 
Asa Gray in reference to plants and by Mr. Darwin as to animals, viz. 
That the migration of forms to which is due the community of types 
in the Eastern States of Isorth America and the Miocene of Europe, took 
place to the North of the Pacific ; an overland communication, it may 
be supposed, having existed during the Tertiary time somewhere about 
Behriug's Straits or the line of the Aleutian Islands. This view is 
confirmed by the occurrence of Miocene vegetable remains in North-west 
America (including genera 3'et growing in Japan but lost to America), 
which prove, further, the temperature of these latitudes to have been 
at that time sufiiciently high to have permitted their existence so far 
north. 
The evidence in favour of the 'Atlantis ' might, moreover, be expected 
to have been more marked in the existing vegetation of the Atlantic 
Islands than is the case. Professor Heer points out the genera Clethra, 
Bystropogon, Cedronella, and Oreodaphne as common to the Atlantic 
Islands and America. Japanese species, however, have been described of 
Clethra and Cedronella ; and Messrs. Webb and Berthelot limit Bystro- 
pogon to Atlantic Island species. Oreodaphne occurs in South Africa 
and adjacent islands. 
A connection between these Islands and Europe, at perhaps a late 
period of the Tertiary, may be considered as highly probable from the 
predominance of Mediterranean forms in their flora. The few genera 
characteristic of the Tertiary which they possess may have been derived 
during this connection ; but the hypothesis that a continent should have 
extended westward as far as America, the speaker considered the available 
Botanical evidence did not in the least substantiate. 
PoTAL Institution of Great Bkitain. — May 23. — " On Coal." By 
Wariugton W. Smyth, Esq., F.R.S. The speaker selected one portion 
only of this large subject ; and, neglecting chemical and statistical and 
mining particulars with reference to this important mineral, confined him- 
self to the ph3'sical conditions under which it is found to occur. 
Mr. Smyth described the nature of the various substances with which 
the coal is associated ; and comparison was made between the total thick- 
ness of carboniferous rocks or coal-measures of different districts, as well 
as between the total thickness of coal (in the aggregate of the seams) ; 
hence we have one reason for not estimating the value of a coal-field merely 
by its area, as laid down in a geological map. Thus, the well-known Dur- 
ham field, with a thickness of measures of about 2000 feet, has a total 
thickness of coal of 50 feet ; the Derbyshire, 2000, and almost twice the 
thickness of coal; the North Staffordshire, 6000 feet of measures, and 130 
of coal ; whilst the South Welsh and Saarbrucken fields exhibit thicknesses 
of 12,000 to 15,000 feet, with a proportionate increase, especially in the 
latter, of coal. A second reason for mistrusting area as a criterion of the 
importance of a coal-district, is the various forms into which the coal-mea- 
sures have been thrown or moulded by agencies operating at a later date 
in the earth's crust, whence some districts may exhibit by outcrops an in- 
dication of the full amount of their entire contents, whilst in others the 
beds pass with a gradual inclination beneath newer formations, through 
