388 
POPULAR SCIENCE REVIEW. 
town) the inclination of the beds is towards the SW. or in the 
direction of the town, the amount of the inclination beiug at 
first 22°. At a short distance the dip is found to increase to 
35° in the same direction. A little farther on, however, the 
amount of the dip being nearly the same (40°), the direction is 
reversed. This indicates an axis of elevation, or, as it is called, 
an ‘^anticlinal axis.” The beds lie like the ridge of a saddle. 
Up to this point the dips have been taken in a railway, cutting 
through a hill, but beyond this the cutting ends. The next ob- 
servation is on the banks of a stream crossed by the road. It 
shows 26° NE. Another hill is now cut through by the rail- 
road near the top of this hill, in a quarry where there is a good 
observation showing a dip of only 20°. In the cutting beyond 
the amount is reduced to 18°, and on the roadside still farther, 
nearly out of the map, the dip is found to be only 14°. All 
these latter dips are in the same direction (NE.) or nearly so. 
It is not difficult to translate these observations into a geo- 
logical phrase, by constructing the section given in fig. 2. An 
outline of the surface marking the differences of level being 
obtained, either from contour lines on a map or from observa- 
tions by an aneroid barometer, the various dips are marked by 
drawing lines, making proper angles with the horizontal base of 
the section ; and the rocks having been noted in each case, these 
may be marked in by lines or colours as most convenient. The 
result is a true section available for reference, and yielding suf- 
ficient account of the geological facts to lay the foundation of a 
geological description. 
It is not easy to imagine a simpler m.ethod of recording ob- 
servations of the nature and relative position of strata than 
sections of this kind. A number of such sections, taken at 
intervals of some miles asunder in a country not greatly dis- 
turbed, will give the material for constructing a geological map, 
and a map thus constructed contains in fact the record of a 
number of observations precisely the same in their nature as 
those from which sections are , obtained. When the sections 
indicate frequent changes in the angle of inclination, whe- 
ther in amount or direction, the observations must be more 
frequent, and the nature of the rock itself must be watched with 
greater care. 
Together with sections such as we have just described, there 
are sometimes means of obtaining accurate observations as to 
the exact nature and thickness of the rocks in a district where 
miuing work is carried on. In sinking a shaft for a well we 
obtain also this result. A section of this kind is called a 
vertical section, and is illustrated in fig. 3. The shaft section 
there given is that of a coal mine, and in this way accurate 
knowledge is obtained of the sequence of the rocks ; so that by 
