May 12, 1870] 
‘© Thus the limit given by Thomson, although so vastly below 
that afforded by the speculations of some geologists, would 
appear itself to demand a considerable additional reduction. 
And I cannot see how we can well suppose the sun in its present 
form to haye radiated heat for more than twenty millions of years, 
while three or four millions would seem to be a far more pro- 
bable estimate, unless the thermic laws be totally different in 
those exalted temperatures which we must suppose to have 
existed at some past epoch. 
‘The very great diversity of the limiting values for the specific 
heat seems to afford ample scope for every needful allowance on 
account of the natural action of the particles within the body of 
the sun, even conceding to this the immense effect (analogous to 
the increase of specific heat) which has been assigned to it by 
some investigators. Even did we conceive a primitive heat equal 
to 200,000,000 times the amount now yearly radiated, and a 
specific heat 10,000 times as great as is possessed by any known 
gaseous body excepting hydrogen, we could not deduce so long 
pected as 80,000,000 of years for the past duration of the sun’s 
heat. 
SCIENTIFIC SERIALS 
THE Geological Magazine for May (No. 71, or Vol. vii., 
No. 5) commences with a biographical sketch of Mr. G. 
Poulett Scrope, whose inyestigations into the phenomena of 
vulcanicity certainly entitle him to a distinguished place 
among eminent living geologists. This article is illustrated with 
an admirable portrait. Mr. Jenkins communicates an article 
on the surface geology of Belgium, in explanation of his 
map, a reprint of which appeared in the April number of 
the magazine. Mr. Maw notices two sections on the borders of 
Shropshire and Cheshire, in which Rhzetic beds with character- 
istic fossils are exposed. In a paper on the Lower Silurian rocks 
of Galashiels, of which only the first part, illustrated with a map, is 
here published, Mr. Lapworth furnishes an important contri- 
bution to the elucidation of this confused group of rocks. The 
article in this number which will be generally read with most 
interest is one by Mr. James Croll, upon the boulder clay of 
Caithness, which he maintains to be a product of the action of 
land ice. This paper also is incomplete. Professor Rupert 
Jones notices and figures the species of Entomostraca from the 
coal measures of South Wales; several of the species are 
described as new. Lastly, Mr. Judd’s paper, on the use and 
application of the term Neocomian, contains a good discussion 
of a matter which, although it seems to be merely a question of 
terminology, is really, especially at the present moment, one of 
considerable importance to geologists. Besides the usual reviews, 
notices, &c., the present number contains a supplementary paper 
by Mr. Samuel Hyde, on deep-mining in the south-west of 
Treland, which possesses much economical interest. 
THE /0is, a Quarterly Journal of Omithology, New Series, No. 
22, April 1870. (Van Voorst.)—This number contains :—(10) 
**Notes relating chiefly to the Birds of India,” by Mr. Blyth— 
the results of an examination of the specimens in the Leyden 
Museum ; (11) ‘* Note on the Systematic Position of Zdicator,” 
by Mr, P. L. Sclater ; (12) ‘‘Stray Notes on Ornithology in 
~ 
India,” by Mr. Allan Hume ; (13) ‘‘ On New and Little-known 
Birds collected during the Voyage of the Magenta,” by Drs. 
Giglioli and Salvadori; (14) ‘‘ A List of the Birds of Turkey” 
(continued), by Capt. Elwes and Mr. T. E. Buckley ; (15) ‘‘ On 
Rare and Little-known Zimicole,” by Mr. J. E. Hasting, deter- 
mining and discriminating two puzzling species of Zudromias, E. 
asiaticus, and E. veredus ; (16) “ On the Oriolide of the Ethiopian 
Region,” by Mr. R. B. Sharpe—a very elaborate article ; (17) 
5 ‘On the Omithology of Hainan” (continued), by Consul Swinhoe ; 
(18) i On existing Remains of A/ca imsennis,” by Prof. Newton, 
showing that-there remain to us of this supposed extinct bird 71 
or 72 skins, 9 skeletons, detached bones of 38 or 41 individuals, 
and 65 eggs. (19) ‘‘ Notices of Recent Ornithological Publica- 
tions””—English, French, Dutch, German, Russian, and Ame- 
rican, wherein more than twenty works are briefly reviewed; and 
(20) ‘‘ Letters, &c.,” from Messrs. Layard, Hume, Brooks, and 
R, Gray, Col. Tytler, Lord Walden, Mr. C. Horne, Capt. 
Fielden, Herr yon Pelzeln, Dr. Salvadori, and Messrs. P. L. 
Sclater, Harvie Brown, Hawkins, H. Saunders, Elliot, Tristram, 
and Skeat—the last a communication which will interest others 
than ornithologists, for it explains the etymology of the name 
* Grey Lag Goose”—the goose that /agged behind the others bred 
NATURE 
5 
ies) 
in this country when its congeners had departed for their suminer 
quarters. The number is illustrated by some woodcuts, and by 
five beautiful coloured plates, by Mr. Keulemans, representing 
eight species of birds, of which six have never been figured before, 
and the other two in imperfect plumage only. 
SOCIETIES AND ACADEMIES 
LONDON 
Royal Society, May 5.—The Bakerian Lecture, ‘On 
the Pre-Carboniferous Floras of North-Eastern America, with 
especial reference to that of the Erian (Devonian) Period.” 
By J. W. Dawson, LL.D., F.R.S., &c., Principal and Vice- 
Chancellor of M‘Gill University, Montreal. 
The attention of the author was first directed to the Devonian 
as distinguished from the Carboniferous flora, by the discovery, 
on the part of Sir W. E. Logan, in 1843, of some remarkable 
remains of plants in the Sandstones of Gaspé, Canada. In 
1859, after visiting Gaspé to study these plants 7 situ, de- 
scriptions of them, and more particularly of the two cha- 
racteristic Lower Devonian genera Prototaxites and Psilophyton, 
were published in the Journal of the Geological Society. 
Subsequently additional material was obtained by personal 
investigation of the Devonian of Maine and New Brunswick, 
and through the kindness of Prof. James Hall, from that of New 
York. These additional plants were also published in the 
Journal of the Geological Society. Still more recently, a 
thorough re-examination of the Gaspé beds, the systematic 
exploration of the plant-bearing beds near St. John by Prof. 
Hastt, and fresh collections made by Prof. Hall, have enabled 
the author to prepare a catalogue of 121 species, and to attempt 
a thorough revision of the Erian flora, and an investigation of 
its conditions of growth and relations to the Carboniferous 
flora. 
The term ‘‘ Erian” is applied to the formations included be- 
tween the top of the Upper Silurian and the base of the Car- 
boniferous, on account of the uncertainties which have attended 
the subdivision and limitation of the Devonian of Europe, and also 
on account of the immense area occupied by these beds on the 
south and west of Lake Erie, and their admirable development 
with regard to subdivisions and fossils. The name ‘‘ Erie Divi- 
sion” was also that originally applied to this typical series by 
the geologists of the Survey of New York. 
A large part of the paper was occupied with the revision of 
the Erian flora, including the description of twenty-three new 
species, and more ample descriptions of others previously known 
only in fragments. Large trunks of Prototaxites, from the base 
of the Lower Devonian, were described, and full details given 
of the form, structures, and fructification of two species of 
Psilophyton, The new genus Ormoxylon was described. The 
genus Cyclostigma was noticed, as represented by two species in 
America, and its foliage and fruit described for the first time. 
The genera of the Erian Ferns were examined and corrected, and 
several interesting trunks and stipes belonging to Tree-ferns were 
described. The fruits of the genus Carvdiocarpum were illustrated 
with reference to their structure. The occurrence of Lepidophloios, 
Calamodendron, and other forms in the Middle Devonian was 
noticed for the first time. 
The third part of the memoir was occupied with comparisons 
and general conclusions. At the close of the Upper Silurian 
period there was a great subsidence of the land in Eastern 
America, proved by the wide extent of the marine beds of the 
Lower Helderberg (Ludlow) group. It was on the small areas 
of Lower Silurian and Laurentian land, remaining after this 
subsidence, that the oldest land plants known in the region 
flourished. Re-elevation occurred early in the Devonian 
period, and the known flora receives considerable extension 
in the shallow-water beds of the Lower Erian. The subsi- 
dence indicated by the great Carboniferous limestone inter- 
rupted these conditions on the west side of the Appalachians, 
but not on their eastern side. At the close of this we find the 
rich Middle Devonian flora, which diminishes toward the close 
of the period ; and after the physical disturbances which on the 
east side of the Appalachians terminated the Erian age, it is 
followed by the meagre and quite dissimilar flora of the Lower 
Carboniferous ; and this, after the subsidence indicated by,the 
Carboniferous limestone, is followed by the Coal-formation flora. 
If we compare the Erian and Carboniferous floras, we find 
that the leading genera of the latter are represented in the 
