April, 1905. 



KNOWLEDGE & SCIENTIFIC NEWS. 



75 



nitrogen atom, and that the magnets in the water are 

 hydrogen atoms. 



N'ow switch on the current and observe the floating 

 magnets; they all approach the " nitrogen atom " up to 

 a certain distance and no further. The movement is 

 very decided at first, but slows down gradually up to 

 the said point. Move the " nitrogen atom " round so 

 that the movable magnets (" hydrogen atoms ") are 

 in a direct line with the electro-magnets and the move- 

 ments of the former obey the ordinary laws of magnetic 

 repulsion. 



The experiment seems to point out that the condi- 

 tion essential to stability in chemical combination is 

 that " the attraction of one atom to another (or others) 

 increases as the distance increases." It is thus the 

 opposite to the law of inverse squares. 



It would also seem to show that combination is only 

 effected when the atoms have taken up a definite posi- 

 tion one with another. 



We may suppose an atom to have around it certain 

 regions which are habitable by other atoms, and when 

 the former are occupied by the latter a stable body 

 results. 



This would harmonise with our ideas of valency and 

 make the suggestion reasonable, that an element may 

 be polyvalent, since it is supposed to have so many 

 " valency regions " which may or may not be occupied 

 by other atoms. 



A carbon atom is said to have four such valency 

 regions. If, now, two carbon atoms are brought to- 

 gether in such a way that one valency region of one 

 carbon atom comes into intimate contact or coincides 

 with one valency region of the other carbon atom, then 

 the region referred to is rendered uninhabitable; the 

 two carbon atoms are held together by a force which 

 obeys the law enunciated above, and we get a ready 

 and adequate conception of the constitution of ethane 

 C, H,;. Similarly when two " valency regions " of 

 the carbon atoms coincide we get the constitution of 

 ethylene C2 H4, and when three (since the regions must 

 not be supposed to be in one plane), we get the con- 

 stitution of acetylene C2 H2. 



So little is known about the properties of electricity 

 that it may be doubted whether the atoms are, indeed, 

 electrified; but apart from the mathematical calcula- 

 tions based on that assumption, which confirm all the 

 known facts, there are other sources from which evi- 

 dence can be drawn, one of which is especially worthy 

 of attention : — 



" Solutions of certain compounds are observed 

 to rotate the plane of polarization." 



If atoms are charged, the explanation of this 

 phenomenon is simple and straightforward. If, how- 

 ever, the assumption is rejected, the explanation be- 

 comes complex and unsatisfactory. 



For many years the scientific world has been satisfied 

 with its conception of the atom as first taught by 

 Democritus and afterwards strengthened by Dalton as 

 a result of his quantitative experiments. 



This conception successfully grappled any difficulty 

 that could not be explained except by assuming that 

 the atom was a small indivisiljle particle. 



It is only comparatively recent research in physics 

 that has demanded its sub-division, and although this 

 does not effect its definition as far as the chemist is 

 concerned, yet others may ask " Can this corpuscle be 

 divided? " Shall we hear some physicist in later years 

 expatiating on the structure of this corpuscle, or shall 

 we be told that now we are as far as we can go, since 

 the corpuscle is the smallest mass conceivable? 



How Britain, becscme 

 IsldLiid. 



an 



By Edward A. Martin, f.g.s. 

 Author oj "A Bibliography of Gilbert White,' &-c. 



There are few phenomena which appeal to the 

 imagination so vividly, and bring to mind the solid 

 geological fact that what is now land was not always 

 dry land, and that where now rolls the open sea was 

 not always covered by the waters of the ocean, than 

 what is known to sea-faring men as the Dogger Bank. 



As a geologist, one is frequently being asked 

 whether it is a fact that this or that place in which 

 the questioner happens to be interested for the time 

 being was at one time beneath the sea. Those who 

 have not grasped the great geological truth that the 

 level of the land-surface has constantly changed in 

 the past, and even now, in many parts of the world, 

 \i undergoing either subsidence or elevation, fre- 

 quently express considerable surprise when they learn 

 that the earth's crust is continually subject to vertical 

 movements; and greater surprise still is shown when 

 it flashes upon them as a geological fact, that Great 

 Britain was not always an island; and that since the 

 time that our country was inhabited by mankind, it 

 had a continental existence, being, in fact, but a 

 portion of a north-western extension of the continent 

 of Europe. 



Although, at a later period in its history, England 

 formed a peninsula which was connected with Europe 

 only by a narrow neck where now are the Straits of 

 Dover, yet, at still earlier time, we have ample evidence 

 to show that Ireland was joined to Great IBritain, and 

 the latter to Denmark and Scandinavia. Tliis could, 

 of course, only be so when all those now isolated coun- 

 tries formed portions of a vast plateau, when the sea- 

 board was at some considerable distance from the 

 present coast, and the whole was at a much greater 

 elevation above the sea than now. 



It is a well-known fact to mariners that when they 

 pass out of the English Channel into the Atlantic, in 

 a comparatively short distance they pass from shallow 

 depths to those which are ten times as great. The 

 same experience is gained in going west from any 

 point on our west coasts, and also in a northerly 

 direction from the north of Scotland. But it is very 

 different on our eastern coasts. With exception of 

 a narrow strip off the Norway coast, which would ap- 

 pear to have been at one time the bed of a rapidly- 

 flowing river with considerable power of excavation, 

 the whole of the North Sea is shallow, as compared 

 with the depths found in other seas of the same mag- 

 nitude. 



If we look at one of the hydrographical maps of the 

 Admiralty, we shall see that the hundred-fathom 

 line is found some little distance beyond the north of 

 Scotland, and that thence it proceeds in an easterly 

 direction almost to the coast of Norway, leaving the 

 North Sea to the south of it, and all of that sea en- 

 closed within that line is under 100 fathoms, or six 

 hundred feet deep. This is a very shallow depth for a 

 sea of the size of the North Sea. 



Now follow the same loo-fathom line around_our 

 west coasts, and we find that it proceeds some consider- 

 able distance bevond the outermost of the Hebrides, 



