OCR Text |
Show CONVERSION OF FORESTS (Ch. XIII. removed by insects, or by putrefaction; but, in the cold temperature now prevailing in our latitudes, many examples are recorded of marshes originating in this source. Thus, in Mar forest, in Aberdeenshire, large trunks of Scotch fir, which had fallen from age and decay, were soon immured in peat formed partly out of their perishing leaves and branches, and in part from the growth of other plants. We also learn that the overthrow of a forest by a storm, about the middle of the seventeenth century, gave rise to a peat moss, near Lochbroom, in Ross-shire, where, in less than half a century after the fall of the trees, the inhabitants dug peat:;... Dr. Walker mentions a similar change when, in the year 1756, the whole wood of Drumlanrig was overset by the wind. Such events explain the occurrence, both in Britain and on the continent, of mosses where the trees are all broken within two or three feet of the original surface, and where their trunks all lie in the same direction t. Nothing is more common than the occurrence of buried trees at the bottom of the Irish peat-mosses, as also in most of those of England, France, and Holland; and they have been so often observed with parts of their trunks standing erect, and with their roots fixed to the sub-soil, that no doubt can be entertained of their having generally grown on the spot. They con· sist for the most part of the fir, the oak, and the birch ; where the sub-soil is clay, the remains of oak are the most abundant; where sand is the substratum, fir prevails. In the marsh of Curragh, in the Isle of Man, vast trees are discovered standing firm on their roots, though at the depth of eighteen or twenty feet below the surface. Some naturalists have desired to refer the imbedding of timber in peat mosses to aqueous trans· portation, since rivers are well known to float wood into lakes ; but the facts above mentioned show that, in numerous instances, such an hypothesis is inadmissible. It has more· over been observed that in Scotland, as also in many parts of the continent, the largest trees are found in those peat mosses "' Dr. Rennie's Essays, p. 65. t Ibiu. p. so. Ch. XIII.] INTO PEAT-MOSSES. fl13 which lie in the least e1 e vate d reer.w ns d th h proportionably sm ll . o ' an at t e trees are a er m those which 1' h' from which fact De L d Ie at tgher levels; uc an Walker h b h · the trees errew on th .l' ave ot mferred that E> e spot, J.Or they would t 11 greater size in lower and wat .m er 1c vels Thn a1 ura y attain a 1 fruits of each species, are continuall f, ~ eaves as~, and moss along with the parent t y ~und Immersed m the and acorns of the oak th rees, as, wr example, the leaves ' e cones and leave f h fi nuts of the hazel. 5 0 t e r, and the Sometimes, in the same b er . . . different k · d f 00 ' a stratificatiOn IS observed of m s o wood, oak being fou d . h 1 stratum, and birch and h 1 . 11 aze m a second bemd tb e owermost times still hio-he a ove. Some-the boer my~le r(,; st~·atum,l containing alder with the twigs of . o yrzca gam), have been found*. 1 " ccsswn of strata in th · . . . . , t 1e sucsion of a dry tra~t int Is mstance, mdicatmg a gradual conver .. Tl . o a swamp, and lastly a peat-moss 1e durability of pine-wood which. . exceeds that of the birch and o~k is m the Scotch peat-mosses of turpentine which it contains 'd d~e t~ the great quantity the fir-wood from boer . d,ban whiCh Is so abundant that os Is use y the count 1 · of Scotland, in the plac e of can dl es Sucrhy peo. p e, m lp arts observes Dr. Macculloch as fir . resmous pants, thaln oak, because the re~n itself :::~ve~;::~~;o ~i:atter ctoal n Hatfield-moss which a umen . forest eighteen hund~ed £ ppears clearly to have been a . years ago, fir-trees have b .l' mh nety feet long , .a nd so ld f,o r masts and k·e els of shei en .J .Ooauknds ave also been discovered th b ps ' 'rhe dimensions of an k fere a ove one hundred feet long. oa rom this m · . Philosophical Transactio N 9l o.ss are given m the larger than any t. ns,. . o .. 75, wluch must have been I ree now existmg m the British d .. n the same moss of H tfi ld . omnuons. d . a e ' as well as m th t f K' 1ne and several oth R a o mcar-to the depth of eierht ~rs,t b oman roads have been found covered o ee y peat All ... he . other utensils f<fund . B .. h. L coms, axes, arms, and R m ritis and Fren h oman ; so that a considerabl . c mosses, are also • . e portiOn of the European peat- Llb, Ent• K no w., T1' mbet Trees p 32 t s 1 • • yst. of Geol.1 vol._ii.,p. 356. |