May 4, 1883.] 



KNOWLEDGE 



269 



A GEOLOGICAL EXCURSION. 



By Grant Allen. 



ONE day last week, ha\-ing nothing in particular to do 

 (a rare complaint with public writers), and having 

 exhausted all the available walks in our own immediate 

 neighbourhood, in space and time, it struck me that it 

 would not be a bad idea to jump backward over a few 

 hundred million years or so at a bound, and take a short 

 holiday excursion in paheozoic Britain. This idea was 

 largely suggested to me by the fact that Dr. Hull, of the 

 GeologicalSurvey of Ireland, has lately publislied a series 

 of charts which enable intending tourists to make their own 

 way through that distant region with comparatively little 

 expense or trouble. So, with a friend to accompany me, 

 and a good map in my hand, I set out boldly on my 

 travels across the ages in a small steam-yacht, whose 

 whistle and screw were certainly calculated both to sur- 

 prise and alarm the unsophisticated inhabitants of the 

 primxval seas through which we sailed. 



Having our choice of all terrestrial time before us, we 

 decided to make our trip in that epoch which Dr. Hull 

 describes as Devono-Silurian, the one, namely, when the 

 massive Old Red Sandstone deposits of Scotland were first 

 laid down. For this purpose, we started our yacht from a 

 port in the North of France, where we found a consider- 

 able mainland stretching east and west, into Germany, on 

 the one hand, and over what is now the open Atlantic on 

 the other. Due north of us, however, a wide sea occupied 

 the central bed of the English Channel, bounded to the 

 south by the continental land on which we then stood. 

 We steered our course straight for the Isle of Wight ; 

 but when we had reached the spot where Ryde 

 usually stands, I was surprised to find nothing but a 

 blue sea still stretching in front of us over the whole 

 area of southern England. I observed to my friend 

 that this was \ery curious, as I didn't remember that 

 there were any strata of corresponding age in that part of 

 modem England, as one would naturally expect if it had 

 once been occupied by a Devonian sea ; the only deposits 

 of the sort that I knew were in North Devon, lying just 

 around the Foreland point My friend, however, at once 

 reminded me that such strata really extended over all the 

 south coast from Cornwall to Kent, only they were con- 

 cealed by overlying deposits of later age, and could not be 

 recognised except by means of deep borings. " There could 

 be no doubt," he said, " that these buried sediments were 

 laid down by the very sea over which we were then sailing; 

 and from the nature of the sediments, and the manner in 

 which they were deposited, he had no hesitation in con- 

 cluding they had been derived in part from land lying over 

 in the direction where Norfolk and Lincolnshire are now 

 to be found. By turning our bows towards that quarter, 

 therefore, he hoped before long to arrive at a contemporary 

 land-surface of considerable extent 



In pursuance of these views, we sailed on over the whole 

 valley of the Thames, with open sea stretching away to the 

 west of us, as far onward as Wales and Ireland. We noted 

 in passing that the sea contained a few strangely-armoured 

 fish, and a good many cephalopod mollusks ; but we, of 

 course, observed that none of the aquatic mammals were 

 yet developed, and that the fauna generally seemed of a 

 decidedly low and unspecialised type. On reaching Warwick- 

 shire and Northamptonshire, however, we saw a low shore 

 lying dimly in front of us ; and my friend pointed out to 

 me that this long penLcsula, stretching westward from a 

 continent which apparently occupied the modern bed of the 

 German Ocean, was part of the land surface from which 



the sediment of southern England was derived ; while in 

 all this part of England, which appeared to us as land, 

 there are, of course, now no strata of this age, as 

 rocks represent the beds laid down under water, but land- 

 surfaces are answered by a blank on the con tern j>orary geo 

 logical map. "By making westward," my friend said, con- 

 fidently, " we shall round the peninsula, and strike through 

 a wide strait up to the Cumberland mountains. Don't you 

 remember that strata of about this age, or a little earlier, 

 run up the whole eastern half of North Waltsl I'm pretty 

 sure the sea in that direction hasn't yet been closed up, and 

 if we run for the Severn valley we shall doubtless find a 

 practicable road." As it turned out, he was quite right; 

 for though we saw high hills on the left already marking 

 the spot where the Suowdon region now stands, we found 

 a clear passage through Cheshire and Lancashire, as far 

 north as the Lake District. There, a mountainous shore 

 stood in front of us, and we found it absolutely necessary 

 to disembark. "The mountains of modern Britain aro 

 already beginning to outline themselves," said my friend. 

 " Though they may perhaps be submerged again more than 

 once in secondary and tertiary times, 1 can plainly see that 

 they will always maintain their relative elevation, and will 

 form at one time islands in the sea ; at another time, sub- 

 marine ridges ; at a third time, mountain chains ; but they 

 will never cease to be comparatively high ground, sur- 

 rounded on either side by lower patches. 



We left our steam-yacht in a little harbour not far from 

 where Durham now stands, and struck our way across the 

 land, still northwards, through a dense forest of curious- 

 looking trees. Most of them were huge dubmosses and 

 waving tree-ferns, interspersed with some wholly extinct 

 types of very tropical and curious aspect. They resembled 

 a forest of horse-tails more than anything else that I had 

 ever before seen. We saw a few conifers, but were not 

 quite certain whether there were any true flowering plants 

 of the higher orders in the place, for though we fancied we 

 noticed one here and there, we could not pick any good 

 specimens to make quite certain, as the light in the woodland 

 was dim and very confusing. There were some odd looking 

 insects, however, all of them very rudimentary, and com- 

 bining traits now only found in quite distinct orders. 

 After traversing this region for about forty miles, we 

 came on the second day to the shores of a large lake. My 

 friend was much delighted when it burst upon us from 

 the summit of a little knoll, covered with scaly Lepido- 

 dendroids, and stiflf, formal calamites. " This," he said, 

 "is clearly the Lake Cheviot of Professor Geikie. From 

 it have been derived the old red deposits of modem 

 Northumberland and Berwickshire. It was once (in upper 

 Silurian days) an arm of the sea, and stretched as far as 

 the Solway Firth ; but I believe we shall now find that 

 end of it dried up, and we shall be able to round it easily 

 at its western edge among the Cheviots. How far it 

 stretches eastward over the bed of the German Ocean, I'm 

 sure I can't say, for we know very little of the submarine 

 deposits in that direction." So, acting on his advice, we 

 turned westward, and successfully got round the corner [of 

 the lake before we had fairly reached the middle of modem 

 Northumberland. 



The southern liill region of Scotland we found chiefly 

 covered by a broad plain, with the same vegetation as that 

 of the country we had already traversed ; and, after three 

 days' good walking through a more than tropical jungle, 

 we arrived at last at the shore of a second and much larger 

 lake. "This," my companion exclaimed, "is clearly 

 Geikie's Lake Caledonia. It is the largest one of all 

 these great inland seas, but I hope its water is fresh, or, at 

 least, scarcely brackish. It will be useless for us to think 



