May 9, 1872] 



NATURE 



25 



What is trae of Iceland is also true of Norway, in the most 

 northern parts of which we find many names compounded with 

 tile Norse word for barley, proving, as the best authorities agree, 

 that barley then grew where it grows no longer. In Scotland 

 many places show signs of the plough, and of having been sown 

 with cereals where arable farming is now unpractised. It is 

 notorious that not only in Scotland, but even in England as far 

 south as Lancashire, large districts that were once covered with 

 forests are now entirely bare of trees, and not only so, but trees 

 cannot be made to grow there. " The Romans planted vine- 

 yards and made wine in parts of England where the hop will 

 now hardly grow." 



In Northern Russia beyond the Dwina there is a vast area, 

 formerly known as Biarmia, studded with the graves and other 

 remains of a very prosperous people, whose wealth and civilisa- 

 tion are much descanted about by the Saga writers. Othere, 

 the navigator, whose story was translated by Alfred, tells us that 

 it was on arriving in their country after the dreary voyage round 

 the North Cape, that he first again met with tilled fields and an 

 agricultural race. This area is now deserted except by a few 

 hunters and fishermen ; the ancient inhabitants have moved west- 

 ward and southward into Finland, &c. I have described the 

 migration in a paper to be printed by the Anthropological Insti- 

 tute. The best authenticated case of this desolation is the in- 

 creased severity of the climate, which makes agriculture almost 

 unendurable there. The Norse traders used to frequent Cholmo- 

 gorod, the port of Biarmia, in great numbers, botli for traffic and 

 for fishing. This navigation continued until the early part of the 

 thirteenth century, when we are told it was gradually put an end 

 to by the increased difliculties with the ice in the White Sea, 

 which becomes practically choked with ice ; and when the Eng- 

 lish found their way to Archangel in the sixteenth century, so 

 forgotten was this old trade, that the journey was treated as one 

 of discovery. 



Farther east facts are less accessible. The following quota- 

 tions from von Wrangel's voyage illustrates my position : — 



" In iSio Hedenstrom went across the tundra direct to 

 Utsjansk. He says, 'On the tundra equally remote from the pre- 

 .viv// ////i' <y /;-<vi among the steep sandy banks of the lakes and 

 rivers, are found large birch trees complete with bark, branches, 

 and roots. At first sight they appear well preserved, but on 

 digging them up they are found to be in a thorough state of de- 

 cay. On being lighted they glow, but never burst into flame. 

 The inhabitants use them for fuel. They call them Adamousht- 

 shina (i.e. of Adam's time). The first livin:.; bireh trees are not 

 lunu found nearer than 3° to the south, and then only as shrubs.' 



' Another cliff, 30 or 35 feet high, beyond the 



Malaya Kurspataschnaja river, consists of ice, clay, and black 

 earth. On drawing out some interspersed roots we found them 

 to be l)irch, and as fresh as if only just severed from the trees. 

 The nearest woods are 100 7'ersts off.' " These facts show how far 

 to the south the limit of trees has been pushed quite in recent 

 times in Siberia, that is, how much more severe the Siberian 

 climate has become — a fact, perhaps, connected with the persis- 

 tent south-westerly drifting of Ugrian tribes from this area which 

 has taken place during the historic period. The flora of our 

 own bogs must disclose evidences of some kind on this subject. 

 I should be thankful to any of your correspondents for facts 

 which illustrate the question drawn from this or any other 

 source. 



Will you allow me to correct two printer's errors in my last 

 letter. Africa has been inserted instead of Arica, and Mine 

 Journal instead of Same Journal, i.e.. Journal of the Geological 

 Society. Both errors due to my execrable writing. 



HeNKY H. IIOWORTII 



A New Mode of taking Casts 



It h.as been suggested to me that an account of "A New 

 Mode of taking Casts," reported in Naturk, May 2, 1S72, might 

 convey the impression that I claimed any share in the invent-on. 

 Modelling wax has been employed for this purpose in Franc by 

 the late At. Edouard Lartet, and I have to thank I'rof. Busk, 

 F. K. S., for having first brought the u-e of the material before 

 my notice. My sole object was to formulate the process ac- 

 cording to my own experience of its utility, that it might be em- 

 ployed by others for the multiplication of type specimens, with- 

 out any idea of claiming its invention. 



W. Boyd Dawki.ns 



Norman Road, Rusholme, Manchester, May 3 



The Denudation of the Mendips 

 In the address of the President of the Geological Society of 

 London reported in Nature No. 129, page 490, it is stated that 

 " Denudation has removed from the crest of the Mendips a mass 

 of strata possibly equal to two miles or more in height, and 

 from that of the Ardennes as much as three or four miles." 



Could you find space to inform me by what reasoning or on 

 what data geologists arrive at such a conclusion, and whether it 

 is considered that the level of the surrounding district was 

 laised in a corresponding degree, or that the Mendips were 

 isolated mountains, somewhat like the Peak of Tenerilfe, rising 

 abruptly from the plains below? Inquirer 



P.S. — Perhaps by inserting this letter and reply you may 

 convey information to others as well as myself. 



Segmentation of Annulosa 



Mr. Ray Lankester, in his letter on " The Segmentation 

 (f Annulosa " in Nature of the 4th ult., appears to maintain 

 that there is no fundamental difference between the segmenta- 

 tion of annelids and that of chitons. lie says of the latter, 

 " Why should there not be segmented molluscs?" I can no 

 more answer this than I could answer the question why there 

 should not be hexapod vertebrates. There is nothing impossible 

 or absurd in the idea of the segmentation of chitons being essen- 

 tially similar to that of annelids ; the question is whether it is 

 really so. He says, " The larva of a chiton is (in appear.ance) 

 identical with that of an annelid, and its segmentation makes its 

 appearance in the same way." This is an important argument, but 

 not conclusive. If, as I believe, Mr. Spencer's theory of the origin 

 of the annulosa is true, the segmentations of the two are funda- 

 mentally distinct phenomena, and it might appear that their de- 

 velopment should be unUke. According to that theory, the 

 segments of the ancestor of the annulosa had their origin by 

 budding backwards from the head ; while the segmentation of 

 the chitons has from the first been " superinduced " like that of 

 the spinal column of vertebrates. But it is admitted that the 

 annulosa do not in their actual development show decided traces 

 of this origin. I think, however, this last fact may be explained 

 by a principle which Mr. Spencer lays down somewhere, with 

 great probability, as a general law (though of course it is a law 

 of tendency only, and may be subject to exceptions), namely, 

 that there is a general tendency to the substitution of direct 

 development for indirect. Thus, the segments of annulosa may 

 have been originally formed one after the other by buddinir 

 backwards, and yet may now be formed simultaneously, or nearly 

 so, by the segmentation of a vermiform larva. 



The opinion that the two cases are distinct is, I think, very 

 strongly confirmed by the fact that annelids still propagate by 

 budding off yourg annelids from thi ir tails, while no mollusc 

 whatever is known to do so. Josern Joh:^ Muri'HY 



Brittany Dolmens and Tumuli 

 In Nature for May 2 Captain Oliver advocates the theory 

 that dolmens are merely the skeletons of original chambered 

 tumuli._ This, I think, scarce'y agrees with the fact to be ob- 

 served in the principal dolmens and tumuli of Finistere. In most 

 cases in that department the dolmens occupy situations in every 

 respect similar to tht se in which the tumuli are found, so that 

 meteorological, and, indeed, every other but human agencie.s, 

 must have affected both in the same manner and degree. Not- 

 withstanding this, the dolmens are invariably b.are, and the kists 

 are as constantly covered — there are no signs of even incipient 

 degradation and denudation in the latter, .and none of former 

 coveiing in the first. It would be unwarrantable to suppose that 

 had the dolmens been uncovered by human beings, no vestitres 

 of the mounds would remain, or that, this perfect and unaccount- 

 able removal of material being allowed, the skeleton, i.e., the 

 part containing the most useful stones, should be left unscathed. 



There is, however, a more important point of difference between 

 dolmens and the barrow kists ; namely, that in the chambered 

 tumuli there is almost always present a floor-stone — a part of the 

 structure which I have never seen at the base of any of the dol- 

 mens of the region in question. And there can, in their case, be 

 no chance of removal, as the floor stone 'would necessarily be the 

 last to remain in its place. The dolmens, again, as a rule, were 

 evidently erected with no attempt at nice adjustment of the sides 

 or tup, whereas tokens of some care and trouble are to be found 

 in the way in which most of the entombed kists are built. 



