June I, 1875^ 



NATURE 



93 



the abomasum, the psalterium being absent. In the 

 Bactrian Camel there is a partial constriction in it, which 

 separates off a small proximal cavity, which may be its 

 homologue. 



In the corpuscles of the blood the Tylopoda are unique 

 among: Mammalia, these minute discs being oval instead 

 o/, as in all other members of the class, circular. 



Of the Camels there are two species, both domesti- 

 cated, the Bactrian and the Arabian ; the one possessing 

 two humps and the other one. A swift variety of the 

 latter is called the Dromedary. The former inhabits 

 Turkestan, Persia, Thibet, and Mongolia ; the latter 

 Arabia and Northern Africa. Of the Llamas there are 

 two wild species which have each of them domesticated 

 representatives ; the feral Guanaco and Vicuna finding 

 their tame representatives in the Llama and Alpaca. 

 They are all found in the Cordilleras of the Andes, down 

 as far as Terra del Fuego. Taking the Tylopoda as a 

 whole, their geographic range is extremely exceptional. 

 Closely allied animals, as the Ostrich and the Rhea, are 

 found in South Africa and South America respectively. 

 North Africa and Arabia, in some respects, resemble 

 India, as far as their fauna is concerned. No similar 

 ties bind Northern Africa with South America, and it 

 is this which makes the distribution of the Camels and 

 Llamas so abnormal and so inexplicable, on the assump- 

 tion that they sprang from a common ancestor as far back 

 as the Miocene age, when we take as our basis the 

 assumption that the existing zoological regions are the 

 remains of a very different distribution of land. 

 {To be continued.) 



THE LINE BETWEEN HIGHLANDS AND 

 LOWLANDS 



THE usual ten days' excursion which terminates the 

 work of the Geological Class at the University of 

 Edinburgh, has this year been devoted to an experiment 

 in the practical teaching of Geology which bids fair to 

 be often and profitably repeated — viz., the working out of 

 a definite problem in the field, teacher and students 

 together. In the Class excursion to Arran in 1872, it was 

 observed that the Old Red Sandstone appeared to be 

 brought against the Highland schists by a fault. Last 

 year the fault was actually seen by the Class on the other 

 side of the island in the cliffs of Stonehaven, Accor- 

 dingly, the task proposed to be accomplished this year 

 was to trace this dislocation across the country, if possible, 

 from sea to sea. Such a traverse would at least bring the 

 pedestrians face to face with some of the finest and least 

 visited river scenery in Scotland, while it would pro- 

 bably also impress some geological lessons on their 

 memory in a way not likely ever to be forgotten. At the 

 same time it might be successful in discovering some 

 new points in British geology. 



The party mustered at Edinburgh, and proceeded at 

 once to Stonehaven, where the first day's work consisted 

 in following the magnificent coast-section which rises 

 above the sea in the picturesque cliffs of Kincardineshire. 

 The fault by which the slates and greywackes of the 

 Highlands have been brought side by side with the 

 red sandstones and shales of the Lowlands was again 

 found. The rocks have there been so greatly squeezed 

 against each other that their line of separation is by 

 no means so abrupt as it might be expected to be. 

 Instead of the mass of ddbris which so often fills up the 

 space between the cheeks of a large dislocation, there was in 

 this case a somewhat tortuous line of junction along which, 

 without any broken materials intervening, the two series 

 of Highland and Lowland rocks seemed to be, as it were, 

 welded together. One might pass this part of the section 

 and fail to notice the fault, though at the distance of a 

 few yards he would find himself in a totally different set 



of rocks, and would then turn back to discover the 

 actual line of separation. That this fault must be an in- 

 portant one was first shown by the fact that the strata of 

 the Old Red Sandstone have here been thrown on end 

 for more than two miles back from their junction with the 

 Highland rocks. Along the noble coast cliffs the beds of 

 sandstone and conglomerate stand on edge like books 

 on the shelves of a library. The portion of them so 

 placed considerably exceeds 10,000 feet in thickness, and 

 yet by no means includes all the Old Red Sandstone of 

 this part of Scotland. 



From Stonehaven the party worked its way across 

 the country for more than 100 miles to the Aberfoyle 

 district. The line of junction between the slates 

 and the Old Red Conglomerates and Sandstones was 

 traced at many points, and sometimes followed for 

 miles across the moors. In no case was the actual 

 fault again seen, but its position could be in most 

 cases drawn firmly on the map by help of the numerous 

 sections laid open by the rivers which descend from the 

 south-eastern slopes of the Grampians. As the journey 

 advanced, however, it was discovered that the fault did 

 not always lie between the Highland rocks and the Old 

 Red Sandstone, but that it sometimes left bays of the 

 latter formation on its north side. This was a new and 

 interesting fact, for it showed the base of the Old Red 

 Sandstone of these regions lying undisturbed and uncon- 

 formably upon the upturned edges of the slates. In these 

 bays were found enormous beds of coarse volcanic con- 

 glomerate and sheets of porphyrite, precisely agreeing 

 with those which form the chains of the Ochil and Sidlaw 

 Hills on the south side of the great valley which here 

 flanks the Highlands. It was, therefore, apparent that 

 the lavas, ashes, and gravels originally extended quite up 

 to and enveloped the base of the Highland mountains that 

 bounded on the north the inland sea or lake in which 

 the Old Red Sandstone was deposited. 



But perhaps the question of most general interest eluci- 

 dated by this excursion was the relation between lines of 

 dislocation and lines of valley. The fault which begins 

 on the east coast at Stonehaven and nms in a straight 

 line across the country to Arran — a distance of 170 miles 

 — is probably one of the greatest, if indeed it is not abso- 

 lutely the greatest, in Britain. We do not yet know the 

 amount of displacement which it has caused. But that it 

 was accompanied by enormous movement of the earth's 

 crust is sufficiently proved by the band of vertical strata, 

 sometimes more than two miles broad, which runs along 

 its southern border. Surely if the valleys and gorges of 

 this country, as many writers still contend, have been 

 caused by or are coincident with lines of subterranean 

 fracture, such a grand line of fracture as this ought to be 

 strikingly characterised by such surface features. Parti- 

 cular attention was devoted to this point during the 

 excursion, and the result may be briefly given. Not a 

 single main valley was found to run along the fault, while 

 all the valleys and some of the deep gorges emerging 

 from the Highlands run directly across it without deflec- 

 tion. In one case only was there an approach to a coin- 

 cidence between the line of the fault and a glen, viz., in 

 that of Glen Artney. But there the dislocation, instead 

 of keeping the centre of the valley, was found to run far 

 up on the northern side, the stream in the centre winding 

 to and fro across the vertical strata of Old Red Sand- 

 stone. Along its whole course the fault is not more 

 marked than on other lines where two series of rocks of 

 different characters and modes of weathering come 

 together. But not only does no long and broad valley or 

 series of valleys mark the line of this fracture in its 

 passage across the island ; it passes athwart the channels 

 of the North and South Esk, the Prosen, the Isla, the 

 Ericht, the Tay, and the Forth, without in the least 

 degree producing any waterfalls or transverse gorges. 

 Moreover, it cuts across^wo of the best known lakes of 



