IS 
rocks descend below the surface may be determined by continuing the 
line of dip where strata disappear to the re-appearance of the same strata 
at a distance in conformity with the curves which are seen in the existing 
beds. 
Thus, if strata be seen to dip at a certain angle, and to disappear below 
the surface, and strata of the same kinds are seen to re-appear in a distant 
part of the country with a dip in the opposite direction, the surface of the 
intervening tract being occupied by rocks of a more recent age, the in- 
ference is fair that the inclined strata are continuous under ground, and 
by connecting the beds at the two extremities by an imaginary line, we 
get a probable section of the strata below the surface. Presuming this 
inference to be legitimate, it may with propriety be applied to explain the 
phenomena connected with contorted strata, the upturned edges of which 
are frequently far apart. 
Applying this principle to the rocks in our own neighbourhood, I cannot 
do better than avail myself of one of Professor Ramsay's sections. The 
section is marked by a line drawn through Dundry Hill, crossing the River 
Avon, and passing by Durdham Down to Blaize Castle., and terminating 
the flats near the Severn, 
In this section, the old red sandstone, the carboniferous limestone, and 
the coal measures are seen to be conformable, and if lines are drawn in 
accordance with the dips and curves exhibited at the surface, it will be 
seen that the strata now denuded must have attained a height of nearly 
8000 feet above the existing sea level. 
The carboniferous strata through which this section passes, is continuous 
on the surface, by Westbury and Henbury ; although interrupted on the 
line of section by patches of old red sandstone and magnesian conglo- 
merate, the former showing that the whole of the carboniferous limestone 
has been removed, laying bare the inferior rock, and the latter exhibiting a 
superficial deposit of new conformable strata, which must have been laid 
down after the older strata had been removed, the deposit of magnesian 
conglomerate lying between the two arms of the range of limestone, being 
probably newer than the carboniferous limestone, (since it is largely made 
up of the debris of that rock), rests immediately upon the old red sand- 
stone. The new red marl, overlain by the lias and the inferior Oolite, at 
Dundry, also occupies a similar position with reference to the carboniferous 
limestone. It is therefore clear that in the one case the carboniferous 
limestone with the superincumbent coal measures, and in the other the 
coal measures themselves have been removed by denudation, prior to the 
deposition of the overlying secondary rocks. 
Our own City and Suburbs present a most instructive illustration of the 
