

ee 

ture 
Dec. 29, 1870] 
NATURE 
177 
a 
of gravity to gravity itself, carried to seven places of decimals. 
The decimal point and ciphers are omitted for convenience. 

Differences of Grayity. 



. Residual errors after correction b 
Relative y 
aa effects of the method of 
. oca 
attraction 4 * 
deduced This Hypothesis. 
from ‘ 
pendulum Dr. Young. 
observations m= 50. | mt = 109. 
Indian are stations. 
Nees ee — 
Bangalore ...| +4384 — 562 = ifs ay) 
Damargiza. . . — 32 — 926 —455 — 584. 
Kalianpur .. . +341 — 208 +338 +315 
Kaliana .,.. — 707 -957 + 69 +320 
Coast stations. 
Punne..... —_— — _ —_ 
AMEDPY J os + 302 +314 +331 + 360 
Mangalore. ..| -—166 —154 —122 -— 79 
Madras... .. —197 —192 — 138 — 78 
Cocanada ... +142 +153 +216 +291 
Ocean station. 
Minicoy Island. | +894 +906 + 31 +102 





The author points out from this table that Dr. Young’s, or the 
usual method of correction for local attraction, so far from im- 
proving matters, introduces very large residual errors of the arc 
and ocean stations; and, at places on the are of meridian, all 
lying on the same side with reference to Punnz. He observes 
that neither the usual method nor his own much affects the coast- 
stations, and attributes this to the want of more complete know- 
ledge of the contour of the surface, both above and below the 
sea-level; in these parts. But his own method, in the case 
mt = 50, remarkably reduces the effects of local attraction at 
stations on the arc of meridian and out at sea (in Minicoy, an 
island 250 miles west of Cape Comorin or Punnz) ; for the 
sensible negative quantity at Damargizea and positive quantity at 
Kalianpur indicate a deficiency of matter below the first and an 
excess below the second—which exactly tally with the results 
independently brought out by relative deflections of the plumb- 
line as obtained by the survey; and the two large and most im- 
portant effects, negative at Kaliana and positive at Minicoy, may 
be said to be almost annihilated by this method of correction. 
This last case of an excess of gravity out at sea (where the sur- 
rounding ocean has a deficiency of matter) being explained by 
his method, he regards as a very strong argument in its favour. 
And he finishes by saying that if his method is thus far successful 
in the particular supposition of the distribution below, whether 
in excess or defect, being wziform, which is most likely not 
strictly the case, there is every reason for concluding that pen- 
dulum-observyations give support to the hypothesis regarding the 
constitution of the Earth’s Crust, when viewed on a large scale, 
admitting of local peculiarities, like the deficiency of matter 
near Damargicea and the excess near Kalianpur, and the similar 
deficiency near Bangalore. 
‘On the Extension of the Coal-fields beneath the Newer 
Formations of England ; and the Succession of Physical Changes 
whereby the Coal-measures have been reduced to their pre- 
sent Dimensions.” By Edward Hull, M.A., F.R.S., F.G.S., 
Director of the Geological Survey of Ireland. In this paper the 
author, embodying with his own the observations of previous 
writers on the physical geology of Great Britain, especially those 
of Murchison, Godwin-Austen, Ramsay, Phillips, and the late 
Professor Jukes, showed that the Coal-measures were originally 
distributed over large tracts of England, to the north and to the 
south of a central ridge or barrier of Old Silurian and Cambrian 
rocks, which stretched across the country from North Wales and 
Shropshire into the Eastern Counties, skirting the southern 
margin of the South Staffordshire Coal-field. This barrier, or 
ridge, was a land-surface till the close of the Carboniferous 
period. To the north of the central barrier, the highlands of 
Wales, the mountains of the Lake district, and probably small 


tracts of the southern uplands of Scotland, formed land-surfaces 
skirting portions of the Carboniferous area, while the Carboni- 
ferous tract to the south of the central barrier was probably 
bounded by a land-surface trending along the southern coast of 
England. The distribution of the Coal-measures at the close of 
the Carboniferous period was illustrated bya map. It was then 
shown that the whole Carboniferous area was subjected to dis- 
turbances through the agency of lateral forces, whereby the 
Strata were thrown into folds along axes ranging (approxi- 
mately) in east and west directions; and as denudation accom- 
panied and followed these disturbances, and acted chiefly over the 
arches (or anticlinals), large tracts were divested of Upper Carboni- 
ferous strata, and thus the first phase in the marking out of the 
limits of our present coal-fields was brought about. The effects of 
these movements and denudations were illustrated by another map. 
The disturbances which ensued after the deposition of the Per- 
mian strata, and which produced the discordances of stratifica- 
tion between the newer Palzeozoic and Mesozoic formations, were 
shown to have acted along lines ranging approximately north 
and south, parallel to the axis of the Pennine Chain, and conse- 
quently in a direction transverse to those of the previous period. 
These disturbances were also accompanied by the denudation of 
strata from off the anticlinal arches, and the consequent dissever- 
ance of the coal-measure tracts over certain definite areas. The 
results of these movements (the second phase in defining the 
bounds of the coal-fields) were illustrated by a third map. From 
a consideration of the foregoing observations, the author came to 
the conclusion that the tendency of the British coal-fields to ar- 
range themselves intu the form of ‘‘ basins ” (sometimes partially 
concealed by newer strata), a tendency strongly insisted on by 
Professor Ramsay, F.R.S., was due to the intersection of the 
two systems of flexures above described, one anterior to the Per- 
mian period, the other anterior to the Triassic period, and that 
the actual disseverance of the coal-fields into basins was due to 
denudation acting with greatest effect along the anticlinal arches 
of these flexures. The inference that the Yorkshire and Durham 
coal-fields are really basins rising to the eastward under the 
Mesozoic strata was drawn—an inference supported by the 
easterly rise of the coal-measures along the sea-coast from the 
Coquet to the Tyne. Guided by these principles, the author 
maintained that we were now in a position to determine with 
great accuracy the actual limits of the coal measures under the 
Mesozoic formations over the area to the north of the central 
barrier ridge, and that to the south of the ridge the application 
of the same principles would assist towards the solution of the 
question, though in a less degree, owing to the fewer oppor- 
tunities for observation of the Palzeozoic formations. The author, 
however, concurred in the views advanced by Sir R. I. Murchi- 
son,” that in consequence of the great amount of denudation 
which the carboniferous rocks had undergone over the area o 
the south of England previous to the deposition of the Mesozoic 
formations, little coal was to be expected to remain under the 
Cretaceous rocks. 
Anthropological Society, December 20.—Dr. Charnock, 
V.P., in the chair. The following were elected Fellows, Mr. H. W. 
Bellew, Peshawur, India; Mr. F. Tagart, F.R.C.S.; and Mr. 
C. Cornish Brown. The Rev. W. W. La Barte, M.A., Local 
Secretary for Brighton. Mr. A. L. Lewis read apaper ‘On 
some Archaic Structures, principally Megalithic, in Cornwall 
and Devon, with remarks on their probable Uses.” The author 
drew a comparison with similar monuments in other places, and 
illustrated the paper by the exhibition of models, from his own 
sketches and measurements, and by photographs. The structures 
described were, a circle called Dance Maen, two circles both called 
“‘Nine Maidens,” three circles together called the ‘‘ Hurlers,” 
all in Cornwall ; and one on Dartmoor, Devon, all which the 
author believed to have been used for sacrifice, and compared 
with some so used in India; ‘‘Chun Quoit,” a sepulchral dol- 
men ; ‘‘ Lanyon Quoit ;”” ‘‘the Spinster,” Devon ; *‘the Treve- 
thas Stone,” Cornwall, used for sacrifice ; the **Men-an-Tol,” 
Cornwall, a monument of perhaps a phallic character, and the 
ancient towns called Chun Castle, Cornwall, and Grimspound, 
Devon.—Dr. Henry Muirhead contributed some remarks on the 
Difficulties of the Theory of Natural Selection. The opinions 
of Mr. A. R. Wallace on the subject were criticised ; and the 
term ‘‘survival of the fortunate” suggested for that of ‘‘ survival 
* In his address at the meeting of the British Association at Nottingham, 
1866. On the other hand, the views of Mr. R. Godwin-Austen, F.R.S., 
which tend rather in an opposite direction, should be well weighed by all 
whoare interested in this question. —Quart. Fourn. Geol. Soc. vol. 
