NovEsrBER, 1902.] 



KNOWLEDGE 



241 



ILLUSTRATED MAGAZINE 



^ai^WJTERATUMJkAir 



Founded by RICHARD A. PROCTOR. 



Vol. XXV.] LONDON: NOVEMBER, 1902. [No. 205. 



CONTENTS. 



» PiOK 



Studies in the British Flora. VI.— The Life and Death 



of Bogs, liv R. Llotd Phakgkb, b.a. (Illustra/eil) .. 241 

 Dr. Aitken on Sunshine and Cloudy Condensation. Bv 



Dr. J. G. i[rPiii:K>.iy, f.r.s.i: .'.. 24-1 



Astronomy without a Telescope. XIX. — The Colours 



of Stars. By K. Walter il.trxDEB, F.R.A.s 2i'> 



Photograph of the Nebulous Region on the following 



side of Gamma Cygni. Bv Isaac Rouebts, d.sc, f.h.s. 



(Plate) ... ■ 247 



The Durham Almucantar. Bv Prof. K. A. Sampson, m.a. 



{Illustrated) .' 247 



The Canals of Mars. By B. W. Laxe. (Illustrated.) 



Witli Note by E. "Walter Mauxdeb, F.n.A.s. ... .. 250 



Chart of Mars. By E. M. Antoxiadi, f.h.a.s 252 



Letters : 



Pekrixe'.s Comet. By R. C. Johxsox. (Illustrated) ... 253 



The Visibility of the Crescent of Venvs. By Joseph 



Offord. Note by E. W. Maunder ... 253 



K.XTINCTION OP QUAGOA. By ThOS. COOPER ... .. 254 



A Modern Ttcho. Br A. "ff. Gabbktt, Lt. R.E. Note 



by E. W. Maunder 254 



British Ornithological Notes. Conducted by Harkt F. 



WrruERBT, F.Z.8., M.B.O.U 254 



Notes 255 



Notices of Books 257 



Hooks Ri!oi;itkd 2.57 



Insect Oddities.— II. By E. A. BrTLER,B.A.,B.sc. (7'HH«<ra/erf) 258 



Microscopy. Conducted by M. I. Cross (IlluntratedJ ... 260 

 Notes on Comets and Meteors. By W. F. Dennino, 



p.h.a.3 262 



The Face of the Sky for November. By W. 



SHACKLBTON, P.B.A.8 2fi2 



Chess Column. By C. D. Lococe, b.a 263 



STUDIES IN THE BRITISH FLORA. 



By R. Lloyd Praeger, b.a. 

 VI.— THE LIFE AND DEATH OF BOaS. 

 When i\ev\i tiirf7euttings in a bog expose the base of the 

 peat anil the beds which uuderlie it, these, as lias already 

 Ijcen jioiuted out, frequently consist of white lake-marls ; 

 in other instances of black mud, the result of marsh con- 

 ditions ; or the ix!at may rest direct on gravel or Boulder 

 clav or solid rock. It may be assumed fairly that a bog — 

 that is, a spongy sphagnous vegetable mass — has generally 

 had its origin in a marsh, which may in its turn have 

 taken the place of a lake or pond. The marginal vegeta- 

 tion of a pond protrudes from the edge as a floating rim, 

 which keeps on growing above, while the lower layers 

 decay and their waste drops to the bottom and slowly 

 builds up a solid foundation for the broadening rim, till 

 the whole is filled with semi-solid ground. Every stage, 

 from the open lakelet full of Charas and Pondweeds, 

 which grow on the limy bottom, to the marsh with its 

 tansrle of Rushes and Sedges, may be studied in any 

 locality where small sheets of water abound. The passage 



of marsh to bog is not so easily found, just as ou the hill- 

 slojws we fail to find fresli ]ieat-bog forming on areas not 

 already covered with peat. The explanation would appear 

 to be that, as a matter of fact, fresh bogs are not forming 

 — but more of this anon. 



We may assume that when our peat-bogs were in their 

 infancy, Sphiujinnii and its associated plants took possession 

 of the ground when marsliy growth had proceeded suffi- 

 ciently far to ensure a permanently wet spongy subsoil. 

 Once bog-growth was started, under the favourable climatic 

 conditions which then prevailed, it may have proceeded 

 with great rapidity, the bog-plants checking drainage, 

 storing ii]3 water, and spreading ever from their centre. In 

 this way the bogs rolled slowly outwards from the marshes 

 or springs where they originated, and eventually over- 

 whelmed great areas that had been well-drained land. On 

 the hills, where higher rainfall gave increased facilities, 

 the bogs spread up and down the slopes, enveloping whole 

 mountain-ranges in a vegetable covering. 



The lower layers of our peat-bogs are usually full of the 

 stumps and roots of trees. The whole of the bog some- 

 times overlies these old forests, which, in such cases, as the 

 roots show, grew on the surface of the clay or gravel which 

 the bog afterwards covered. But in most instances the 

 trees are rooted in the peat, and sometimes successive 

 layers of tree-stumps show that several epochs of forest- 

 growth occurred during the accumulation of the peat. 

 The distribution of these trees, consisting chiefly of Scotch 

 Fir and Oak, buried in bogs, deserves special considera- 

 tion. They are found to extend in Scotland far north of 

 the present limit of the species, while in Ireland, where 

 the Scotch Fir is now extinct as a native, the remains 

 of this tree occurs in enormous quantity throughout 

 the land. In both countries the old forests appear at 

 elevations in the mountains far beyond the present upper 

 limit of the species. Along the exposed western coasts of 

 Scotland and Ireland, enormous stumps may be dug out 

 at various levels where now, even with artificial protection, 

 trees vrill not grow. Not only that, but in numerous 

 places round our shores, between tides, or even far below 

 low-water mark, tree-bearing peat occurs. So that 

 the evidence of the trees of the lower part of our peat- 

 bogs indicates not only a somewhat different climate, 

 which allowed a much wider extension of these forest- 

 growths, but a greater elevation of the land. At Belfast 

 a bed of jwat, with Hazel and Scotch Fir remains, and 

 bones of Red Deer and Wild Boar, occur at 27 feet below 

 high-water mark, and the beds which overlie it prove that 

 subsequent to its deposition a depression of 50 or 60 feet 

 took place, followed by 30 or 40 feet of upheaval.* And 

 not onlv have the sea-beaches and sea-bottom where these 

 submerged trees occur been dry land, but, as Prof. James 

 G-eikie points out,f the luxuriance of the forest-growth 

 which formerly flourished on what is now exposed and 

 treeless coast, shows that at that period the shore-line 

 must have been some distance removed ; " there can be 

 little doubt that at some time during the latest great 

 extension of the European continent, the upraised beds of 

 the Irish Sea, the English Channel, and the G-erman 

 Ocean, were included under the folds of that broad mantle 

 of green forest, the relics of which are so conspicuous in 

 our peat-mosses." Such an extension of the land would 

 undoubtedly assist in supplying the comparatively con- 

 tinental climate and lessened exposure which would 



* Praeger : " On the Estiiarine Clay at the new Alexandra Dock, 

 Belfast." Proc. Belfast Nat. Field Club, 1886-87. Appendix. 



+ James Geikie ; "On the buried forests and peat-mosses of Scotland, 

 and the changes of climate wliich they indicate." Trans. R. Soc. 

 Edinburgh, XXIV., pp. 363-384. 18GG. 



