188 Correspondence—Mr. J. S. Gardner. 
increase of z}5 which takes place at the maximum eccentricity is 
competent to raise the mean temperature of the earth by nearly 2° F.; 
and this increase of heat being maintained for thousands of years 
could not fail to affect the position of the lines of perpetual snow. 
Whether there would be an actual increase of 2° F. in the mean 
temperature I need not discuss, because as regards the formation and 
dissipation of snow and ice the essential element appears to be the 
quantity of heat absorbed in the course of the year. 
13, BenvEpDERE Prace, Dustin, Fed. 27. W. H. L. Moncx. 
ON THE CORRELATION OF THE GRES DE BELLEU WITH THE 
LOWER BAGSHOT. 
Str,—In discussing Prof. Prestwich’s new correlation of our 
Eocenes, I could not help calling attention to the fact that while in 
his table the position of the Grés du Soissonnais would be below 
the London Clay, its Flora coincided with that of our Lower Bagshot 
at Alum Bay, above the London Clay. This apparent anomaly 
is capable of explanation. 
The only comprehensive publication on the Flora of the Paris 
Basin is by Watelet, and though his determinations possess little 
interest, the illustrations are sufficient in most cases for comparison. 
The plants represented therein are mainly from Sézanne and Bellen, 
with a few from other localities. The precise age of the travertins 
of Sézanne is, in the absence of direct stratigraphical evidence, an 
unsolved problem, but the aspect of its flora is so ancient that it is 
difficult not to agree with Saporta, Schimper and others who place 
it in the Pal-eocene. It is in fact allied rather to the newest 
Cretaceous floras of Europe than to any Hocene flora, and its nearest 
representative in our country is the flora of Ardtun in Mull. The 
few plants from the Grés “intercalés dans les Sables de Bracheux” 
and from the Lignites are insufficient to tell us anything, but those 
from the Calcaire Grossier are well-marked Bournemouth species. 
It is with the vast majority, however, from the Grés de Belleu, that 
we have to deal, and these we cannot hesitate in correlating with 
our Lower Bagshot of Alum Bay. The forms common to the two 
are a Fern, the Palms, all those highly characteristic forms called 
Comptonia and Dryandra, the large Ficus Bowerbankii and other 
species of Ficus, Laurus? Salteri, Quercus or Castanea eocenica, a 
supposed Cinnamomum Larteti, the flower called Porana, leaves of 
Acer, and bean-pods of Acacia and Cesalpinia. The Podocarpus 
elegans, Marattia Hookeri, and particularly the Aralia primigenia, so 
characteristic of Alum Bay, are absent, but the two former are 
equally absent in the corresponding beds so close at hand as Stud- 
land. On the other hand, the Belleu beds are far richer in the 
trinerved leaves known as Daphnogene and Cinnamomum. Such 
differences are, however, always met with in separate patches of 
plants, even if on precisely one horizon and near each other, and do 
not suffice to affect the main fact, that the facies of the floras is as 
a whole the same, and very different indeed to any flora above or 
below them. I have had large series of the plants from both 
