70 ' - REPORT—1857. 
the parallel of 52° it would be depressed by 196 feet. Shallow seas and banks in the 
latitudes of the British Isles, and between them and the pole, would thus be converted 
into dry land, while low-lying plains and islands near the equator would be submerged. 
If similar phenomena occurred during early periods of geological history, they would 
manifestly influence the distribution of land and water during these periods ; and with 
such a direction of the forces as that referred to, they would tend to increase the pro- 
portion of land in the polar and temperate regions of the earth, as compared with the 
equatorial regions during successive geological epochs. Such maps as those published 
by Sir Charles Lyell on the distribution of land and water in Europe during the ter- 
tiary period, and those of M. Elie de Beaumont, contained in Beudant’s ‘ Geology,’ 
would, if sufficiently extended, assist in verifying or disproving these views. 
On the Conductivity of various Substances for Heat. 
By Witt1aM Hopkins, W.A., LL.D., PRS. 
The author gave an account of the results of numerous experiments which he 
had recently made on the conductive powers of various substances for heat. To 
explain the object of these experiments, he stated that if a globe of very large dimen- 
sions, like the earth, were heated in any manner and in any degree, and then left to 
cool by the radiation of heat from the surface, the temperature of the mass at points 
not too remote from its surface, and after a great lapse of time, would follow a very 
simple law,—the increase of temperature in descending below the surface would be 
proportional to the increase of deptii—supposing the conductive power of the mass 
to be the same throughout. But if a stratum of another substance (as sedimentary 
matter for instance in the case of the earth) should be superimposed on the sphere, 
its horizontal extent being large in proportion to its thickness, the rate of increase of 
temperature in descending within this stratum, would be greater or less than in the 
other parts of the sphere, according as the conductive power should be Jess or greater. 
It would be very approximately in the inverse proportion of the conductive power. 
The principal object of these experiments was to ascertain whether such be the case 
or not. 
The conductive powers of lime, clay, and sand, in the state of dry powder, are in 
the order in which they are now mentioned. Calcareous rocks from dry chalk to hard 
mountain limestone vary in their conductive powers (on the numerical scale adopted) 
from 1:7 to 5°5; dry sandstone rocks from 2°5 to 7°5; granite and very hard com- 
pact felspathic rocks from 5 to 10. 
Hence it follows, that if the temperature observed at present in mines, Artesian wells, 
&c. be entirely due to heat transmitted from a central nucleus, the rate at which the 
temperature increases in descending below the surface of the earth, ought to be very 
different in different formations. It appears, however, that this rate in those mining 
shafts and Artesian wells which have penetrated to the greatest depths, and in which 
the observations are most trustworthy, in different parts of Western Europe, is nearly 
the same in different formations. ‘The author compared the two cases of the Puis de 
Grenelle at Paris, anda vertical coal shaft at Duckenfield nearManchester. He esii- 
mated the conductive power in the former case at one-half of that in the latter, while 
it was found by observation that there was an increase of 1° I, fur every 60 feet of 
depth in the former, and for about 64 feet in the latter instance ; whereas these depths, 
instead of being in the ratio of 60 : 64, ought, according to the theory, to be in the 
ratio of 60 : 120. This proves that the temperatures observed in these cases cannot 
be due merely to heat transmitted from the interior of the earth by ordinary conduc- 
tion. 
The author stated also that he had investigated the influence of induration, pres- 
sure, moisture, and discontinuity, on the conductive powers of various substances, 
referring for details to a paper lately read before the Royal Society. 
On the Geological Structure of the Dingle Promontory, Co. Kerry. By J. 
Berets Jukes, JA., F.R.S., URLA.; and G. V. Du Nover, ARLA. 
The authors stated that the object of this paper was twofold ;—Ist, to deseribe the 
very singular and interesting structure of the district, and 2ndly, to point out a very ims 
