April 2, 1900.] 



KNOWLEDGE. 



91 



wick, alike connect us with the north. As for the latter 

 name, it carries us awaj- to our own east^country fen- 

 land, where our Chalk also dips beneath the river- 

 alluvium and the marshes, amid English windmills, 

 wherries, and canals. In this open country, as we havo 

 hinted, each city is still a fortress ; we enter by narrow 

 and often winding roadways, between loopholes and the 

 mouths of cannon ; and the tall churches, crowning St. 

 Omer. Laon, or St. Quentin, have looked down upon 

 sieges, and have outfaced many a civil war. The Chalk 

 has much to answer for, in favouring the spread of 

 armies, and in raising no barriei-s to invasion. The fords 

 in the deep valleys have proved difficult to strangers in 

 the past; but Crecy-en-Ponthieu and Azincourt, to 

 name no others, record the failure to dislodge an enemy 

 from the plateaux. 



The broad basin in which Paris lies was formed by 

 folding, at about the same period as our smaller basin 

 around London ; its eastern rim, corresponding to our 



west side of this enormous basin ; where shall wo re- 

 cover it on the south-east, across the Moselle or the 

 Rhone ? 



The folding that has had sucli nuld elTccts in most 

 of the Anglo-Norman area shows here and there far 

 more serious results. West of Guildford, the Ciialk dips 

 at 35°; and in Dorsetshire and the Isle of Wight its 

 beds are in places contorted or even vertical. Similar 

 contortions are well known near Flamborough Jlead; 

 but we now proceed to a district where earth-wrinKiing 

 has actually destroyed our Downs, and has left us only 

 local Cretaceous strips, caught in the synclinal folds. 

 The anticlinals, following closely on one another, consist 

 of Jurassic rocks ; the escarpments of the Cottcswolds 

 and the Cotc-d'Or are repeated again and again in the 

 course of a few miles; and the dip-slopes arc often as 

 steep as the scarps, which are formed by the upturned 

 limestone edges. This region of repeated folding gives 

 us the beautiful parallel ranges of the Juras. Among 



m£ 



?)s" 



FlO. 1. — Summit of tlie Santis, Switzerliind, formed of Upper Crefcai^cous st.rata, with tlie dip-slopo deferniining the mouDtaiu-side 

 upon the left, and tlie escarpment forming the more cnigi^y slope upon tlio right. 



Chilterns, away beyond the vineyards of Champagne, 

 similarly looks out on the back of the French Ccttes- 

 wolds, that is, on the .Jurassic range that runs from 

 Dijon, by Langres and Nancy, into Luxemburg. Be- 

 yond this Jurassic scarp, the Moselle, running north- 

 ward, plays the part of the English Severn. From 

 Gloucester to Dijon, wc may. then, broadly picture one 

 great synclinal curve, formed of the beds of the Cottes- 

 wolds, which rise again and terminate as the bold Cote- 

 d'Or in France; these bear on their backs the wide 

 Chalk Downs, the Vespasian's Camp at Amesbury to 

 Chalons-sur-Marne, the exercising fields of two lost em- 

 pires ; and these Downs wrap round and enclose in their 

 turn the still later beds of London and of Paris. Wc 

 have sought the Chalk again in Antrim on the north- 



the beds involved are some that correspond to our 

 " Lower Greensand " strata, which come out around the 

 English Weald : but in Upper Cretaceous times the 

 Jura ridge had probably already risen, forming a chain 

 of islands in the sea. 



The Alps themselves, however, lay long beneath the 

 ocean. The limestones that represent our Chalk were 

 laid down in a clear sea that stretched unbroken into 

 Syria; and on them the Eocene sea continued to deposit 

 ' nummnlitic limestone," rich in foraminifera and other 

 marine types of life. When the great Alpine niove- 

 mcnts came, which were already foreshadowed in the 

 Juras, the whole Cretaceous series became crumpled 

 together like a cloth. In successive periods, the central 

 Alpine mass moved upwards, culminating at the close 



