169 
hours, and that it was particularly useful in warming a bed- 
room, where only a slight elevation of temperature was 
required, and perfectly free from the production of dirt or 
the slightest smell. 
None of the products of combustion entered the room, 
and the ventilation was improved rather than impeded. 
ON THE EXCAVATION OF THE VALLEYS IN THE TABULAR 
HILLS, AS SHOWN BY THE CONFIGURATION OF YED- 
MANDALE, NEAR SCARBOROUGH. BY H. C SORBY, 
ESQ., F.G.S. 
The Tabular Hills are a range of flat-topped hills, ex- 
tending from Scarbro' westwards to near Thirsk. They are 
composed of coralline oolite, or calcareous grit, at the top, 
overlying Oxford clay, Kelloway's rock, cornbrash, and the 
upper sandstone and shales ; and their peculiar configuration 
is very clearly traceable to this structure. The part to which 
I shall particularly refer is that near Scarbro'. Proceeding 
from the low flat tract of the vale of Pickering, the surface 
of the hills rises gradually to the north for some distance, 
and then the top becomes nearly level, having no undulations, 
and diversified only by deep-cut ravine-shaped valleys ; the 
configuration and origin of which is the subject to which I 
wish to call your attention. 
The nature of these valleys will be best understood from 
Sec. 5, Plate III., where a portion of the level top will be 
seen on both sides, and the ravine-shaped valley cut sharply 
out, with the sides inclined at an angle of 30°. 
We have, therefore, in these valleys a case in which it 
might with considerable propriety be concluded that they 
had been produced by the action of the streams now running 
in them, inasmuch as their form is the same as would be 
produced by such action, continued for a long period. We 
