April, 



1905. 



KNOWLEDGE & SCIENTIFIC NEWS. 



11 



upon its former dominions. The animals retreated 

 farther and farther south, until many of them took 

 lefuge upon the high land of the Dogger Bank. This, 

 in the course of time, became an island, the sea soon 

 enclosing it on every side. In the trawling operations 

 which are constantly going on in the region of the 

 Dogger, many bones and teeth of the mammoth and 

 other animals now- extinct in those regions are con- 

 stantlv being brought up. In fact, scarcely a trawl is 

 brought to the surface that does not contain some of 

 these remains. Now why should they be found there 

 in such abundance? Probably the various currents 

 which were brought into play as the surrounding parts 

 came to the surface may have been responsible for 

 banking up hereon many of the bones, &'c., collected 

 from the area which was sinking into the sea. But 

 there seems also good reason to believe that the Dogger 



Island formed a veritable place of refuge, where were 

 congregated during the last years of its existence the 

 numerous animals who had been driven south, who 

 had here been stranded involuntarily while the ad- 

 vancing sea cut off their retreat. Betw-een the time 

 of its having become an island and its own final dis- 

 appearance beneath the ocean, not many thousands of 

 years may have elapsed. There would be no time for 

 the evolution of fresh species. Those that were first 

 here isolated were of the same kind as those who w^ere 

 finally starved out, or overwhelmed in the advancing 

 waters. There in the end they succumbed, and their 

 remains are now- brought up in the North Sea trawling 

 nets. 



We can pursue the evolution of the British Isles a step 

 further. Britain had by this time received its comple- 

 ment of Neolithic savages, whilst Palaeolithic man, 

 who had seen the advent and disappearance of the great 

 ice age, had also disappeared before the march of the 

 more civilised Neolithic man. Owing to the absence 

 of true glacial formations in England south of the 

 Thames, it is considered that these parts at no time 

 were the nursery grounds of glaciers, and that they did 

 not participate in that great subsidence which visited 

 all those parts which were subjected to the enormous 

 weight of the great ice-sheet. The North Downs were 



all the while continuous from the Forelands and from 

 Folkestone to the Continent, as w-ell as the South 

 Downs from Beachy Head, and the intermediate 

 Wealden Heights from the neighbourhood of Hastings. 



When the sinking took place in the bed of the 

 English Channel, which allowed of the approach of the 

 sea, the action of the waves, aided to an important 

 extent by tide action, soon widened the Channel by 

 eating away the soft tertiary strata which probably 

 covered the chalk. Then attacking the chalk it formed 

 cliffs of this rock, and the work proceeded until the 

 sea had encroached to a point east of Brighton on the 

 British coast, and a corresponding position on the 

 French coast. Here was a pause, to which are to be 

 attributed the raised beaches, which rest upon ledges 

 in the chalk, w-ith the old chalk cliffs behind them. 



But soon the pause came to an end. The sea again 

 advanced, and cut through the beaches it had formed 

 at the eastern end of the English gulf. Thus was lost 

 the connecting sea-margin between England and 

 France. Probably this eastern shore was pierced at 

 more than one place by short rivers, w-hich were then 

 draining the Wealden saddle-back ridge which formed 

 the backbone of the Anglo-French isthmus. Others 

 may have flowed in the opposite direction and have 

 been at one time part of the great Rhine system. Simi- 

 lar ri\-ers piercing our present chalk downs and taking 

 their rise in the Weald are seen in the Sussex Ouse, 

 the .-\run, and .Adur; in the Mole, the Wey, and the 

 Darent; but in these days thev were powerful rivers, 

 and flowed from a greater height than now. 



The advancing sea w-ould creep up the beds of these 

 imaginary rivers, widening their valleys as it advanced. 

 Soon it would reach the low parts of the Weald clay 

 between the two parallel ridges of chalk downs, and 

 the English Gulf and the North Sea would join hands 

 by the connection provided by the river valleys. Thus 

 the chalk hills would be attacked in the rear, and in 

 the course of a short geological period the chalk 

 isthmus would be gradually planed down, and the 

 incipient Strait of Dover become an accomplished fact. 

 Once the passage had been made for the tides, the 

 breach would quickly widen, and the isolation of 

 Britain thus became assured. 



The position gained has been maintained. Britain 

 an island had been the end to which geological agencies 

 had been moving for many thousands of years. Now- 

 the end was gained. Britain an island had become an 

 accomplished fact, and in spite of numerous sub- 

 sequent minor movements she has retained that posi- 

 tion w-hich Nature gave her — an island set in the silver 

 sea. 



Absorption of Mercury Va.pour by 

 Aluminium. 



M. Tarigi has recently been investigatins the power which 

 alumiQium has for absorbins; mercury vapour. This is mani- 

 fest even when the vapour is largely diluted with air. and at 

 the temperature of the surrounding atmosphere. This pro- 

 perty constitutes a very delicate method of analysing the 

 presence of mercury, and furnishes a means of prevention 

 against poisoning by its vapours. .A respirator has been con- 

 structed in which the air, before entering the lungs, has to 

 pass through a mass of finely-pulverised aluminium, and in 

 this way all traces of mercury are absorbed so completely that 

 breathing can be carried on even in the dense vapours pro- 

 duced by the burning of chloride of mercury. 



