NATURAL HISTORY. 
inclination. The valley of the Foyle,—another which nearly insulates the city of Londonderry,— and 
a third in the bishop’s garden (beyond the walls), are good examples. The transverse valleys, 
resulting from broken and rugged edges of the strata, are of comparatively small extent, and form 
the upper surface into gentle undulations. 
Section 2.— Rocks, 8fc., as applied to practical Purposes. 
In this section there is not much to remark upon: it may be noticed under the following- 
heads :— 
1. Building Stones. —The schistose rocks are in the harder varieties too coarse, and in the 
softer not sufficiently coherent for roofing slates; but no deep excavations have yet been made. 
They are, however, used extensively as common building stones, and, when selected from a hard 
variety, are well fitted for the purpose. 
2. Limestone. —This is probably a very limited deposit, and the limekiln in Mullennan, as 
well as the quarry, has been abandoned. The limestone, used at the kilns in the city, is brought 
down the river from beyond the limits of the parish. 
3. Greenstone. —This is quarried extensively for the roads, and, being carried to the river, 
is transported to Derry, where it is broken up at the gaol by the prisoners. It is raised 
for 7 d. per ton, and costs 2s. 9 d. at the gaol, carriage included. Being exceedingly hard, the 
people imagine that it is purchased for the mere purpose of increasing the labour of the prisoners. 
4. New Red Sandstone. —This is used occasionally for grindstones, though rather soft for 
the purpose. 
5. Clays.—' The brick-yards on the Foyle were given up about thirty years ago, in conse¬ 
quence of the growing scarcity of fuel. It is desirable that steps should be taken to supply coals 
to the farmers on the river, as there can be no doubt that the manufacture would then be resumed, 
and much valuable time saved, which is now applied to the cutting and making of turf. 
6. Soils. —The soils in this parish, resulting from the decomposition of the same class of 
rocks, have much uniformity of appearance and composition. In the higher grounds they contain 
more of the silex of the rocks,—and are occasionally, though rarely, stony, sandy, and meagre. 
In by far the greater portion of the parish they are light productive clays, or loams, which in 
the very low grounds become stiffer, though never to an injurious extent. 
7. Bogs. —Though only relics of a much more extensive tract, the bogs are of great local 
importance. In several townlands they supply fuel to the inhabitants, as well as an important in¬ 
gredient in the composts used for manures. Portions are still occasionally reclaimed, and when 
the turf has been totally cut away the sub-soil is readily brought into cultivation. 
Bogs have been already incidentally cited, to illustrate some of the appearances exhibited by 
detritic accumulations. They merit, however, a distinct geological notice, as being one of the most 
recent effects of those modifying agencies, which still continue to operate on the Earth’s surface. The 
vast mass of vegetable matter, spread over so large a portion of Ireland, has at all times attracted 
attention from its magnitude ; and even in this parish, were it possible to restore all that has been 
cut away, and to remove the now verdant surface from the parts reclaimed, about x 0 th would 
be bog. It is natural that a formation so remarkable should be attributed to other causes than 
those now operating by persons, who, beholding merely the accumulated result of ages, do not 
perceive the steps by which that result has arisen; but careful investigation will induce 
more correct views, by showing that what was once done might be done again—the causes which 
then acted being equally efficient now, or, if comparatively inactive, only so in having arrived at 
natural limits, which arrested the further progress of their efforts. In the “ Bog Reports” Mr. 
Griffith states, from his own observation during twenty years, an example of bog having grown at 
the rate of 2 inches every year—an instance probably of excessive growth under peculiarly favour¬ 
able circumstances, yet valuable in its direct testimony to the fact that bog, fitly circumstanced, 
still continues to grow with undiminished vigour. 
In the production of bog sphagnum is allowed on all hands to have been a principal agent, and 
superabundant moisture the inducing cause. To account for such moisture, various opinions have 
been advanced, more especially that of the destruction of large forests, which, by obstructing in 
their fall the usual channels of drainage, were supposed to have caused an accumulation of water. 
That opinion, however, cannot be supported,—for, as Mr. Aher remarks in the “ Bog Reports,” 
“ such trees as are found have generally six or seven feet of compact peat under their roots, 
which are found standing as they grew, evidently proving the formation of peat to have been 
previous to the growth of the trees”—a fact, which, in relation to firs, may be verified in 
probably every bog in this parish, turf from 3 to 5 feet thick underlying the lowest layer of 
such trees. It is, indeed, so strongly marked in the bog, which on the Donegal side bounds the 
road to Muff, that the turf-cutters, having arrived at the last depth of turf, find timber no longer, 
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