202 



NA TURE 



{Jan. 15, 1874 



I hope, be shortly pubUshed, go a long way towards proving it. 

 Accepting this hypothesis, the next question we have to decide 

 is whether the rising of the land lis an absolute or a relative 

 rising ; whether, in fact, the earth's periphery as a whole is un- 

 dergoing enlargement or contraction, is stretching or shrinking. 

 To decide this by direct observation is not ea5y; for water being our 

 only measure, the same effect will be produced either by the link- 

 ing of the one portion or the rising of the other, tha^ is, of course, 

 if the rising or sinking be general ; while if it be a local rising 

 at one place, it may (as is familiarly known, and as I shall point 

 out presently) be due to the lateral pressure caused by an adja- 

 cent subsiding area. In the absence of direct experiment, we 

 may be guided by analogies from other facts. These facts are of 

 two kinds — astronomical and geological. 



Since the days of Laplace, the nebular hypothesis has been 

 generally received by astronomers, as the one which best meets 

 observed facts. This hypothesis predicates the existence of 

 gravitation eveiywhere, and shows how, by its influence, the 

 various heavenly bodies have become condensed from nebular 

 matter. It predicates that this force is still active everywhere, 

 and that everywhere within our observation we have a condensa- 

 tion of matter in progress, matter condensing from a highly 

 diffused condition to one of greater density. Thus each mem- 

 ber of our own system, it is argued, is gradually and surely 

 neaving the sun, and at the same time is shrinking, and the 

 various planets ai"e, in fact, in so many stages of evolution, and 

 exhibit for us the various phases which the earth has passed 

 through and will pass through before it is landed in the sun. 

 This IS all very elementary. I quote it only to show that the 

 evidence of astronomy is that tue earth is contracting, that its 

 periphery is diminishing in area, and that therefore it is probable 

 that the subsidence ol the ocean-bed is absolute, while the 

 upheaval of the land is relative only. 



Geologists argue differently and yet come to the same con- 

 clusion. They argue that the original condition of the earth was 

 an incandescent one, and that it has assumed its present form 

 after a gradual cooling, that is a gradual contraction. In Mr. 

 Geikis's words, recently reported in your pages, "Among the 

 geologists of the present day there is a growing conviction that 

 upheaval and subsidence are — concomitant phenomena, and that 

 viewed broadly, they both arise from the effects of the secular 

 cooling and consequent contraction of the mass of the earth." 

 The evidence of geology, then, is at one with that of astronomy 

 in making the shrinking of the earth absolute and not relative 

 merely. 



Now it is very clear that if the shrinking earth acquired a cer- 

 tain amount of rigidity, such shsinking would cease to take place 

 uniformly, and the crust would give way along certain weak 

 lines, and that corrugations, i.e. mountain-chains, and deep pits, 

 or ocean hollow s, would be formed ; and not only so, but the 

 sinking of a given area would give rise naturally to a certain 

 thrust upwards of a contiguuus area. To quote the graphic words 

 of Mr. Geikie : " Some portions have sunk more than others. 

 These having to accommodate themselves into smaller dimen- 

 sions would undergo vast compression and exert an enormous 

 pressure on the more stable tracts which bounded them. It 

 could not but happen that after long intervals of strain, some por- 

 tions of the squeezsd crust would at length find relief from this 

 pressure by rising to a gi"cater or less height according to their 

 extent and the amount of force from which they sought to escape." 

 From this we may conclude (what I have not seen mentioned 

 elsewhere), that from the contraction of the earth alone we may 

 deduce the result that the land areas have been gradually growing 

 larger and the ocean areas smaller ; that originally when the 

 crust was less rigid, its surface was almost uniformly level and 

 covered with water, and that as it gradually became corrugated, 

 the land fir^t appeared as an archipelago of islands which were 

 gradually joined together into continents in the way Australia 

 was clearly constructed, comparatively recently ; or in other 

 words, that the proportion of subaerial to sub-aquxous deposits 

 must diminish as we recede in geologic time, inasmuch as the 

 area of ser, i.e. of water-covered surface, increases. 



In this statement of the gradual shrinking of the earth there is 

 little that is new, and if it accounted for all the facts I should 

 not have troubled you with another letter. It has been taken 

 for granted hitherto, if I be not mistaken, that areas of subsi- 

 dence and upheaval are scattered about the world in a sporadic 

 manner, with as little order and aim as plums in a pudding ; 

 that the earth being in process of shrinking, areas of subsidence 

 occur at any point where the earth's crust is weak ; but the evi- 



dence which I have collected and which I hope the Geographi- 

 cal Society will publish, goes far to show that these areas 

 are not sporadic Ijut continuous, and further, that the foci of 

 upheaval are in the circumpolar regions. That it is there where 

 we meet with proofs of current and rapid upheaval almost at 

 every step, and the farther we go north or south from the 

 equator the more rapid does the rise seem to be, while 

 in the equatorial regions the land masses are to a great ex- 

 tent quiescent ; we cannot resist the conclusion that the earth is 

 stretching itself in the direction of its shortest axis, that its 

 periphery is being thrust out in the direction of the Poles. Now 

 as we have shown that the earth is absolutely shrinking and that 

 when any local uprising occurs it is due to the lateral pressure 

 caused by a subsiding area, it becomes interesting to inquire what 

 kind of strain upon the earth would produce a squeezing of it 

 out in the direction of the Poles. I can see only one explana- 

 tion, namely, that the strain is being applied in the way of a stric- 

 ture about the world's equatorial region, that it is girdled in that 

 region by some force which is tightening upon it, and this 

 tightening produces a partially compensating protrusion of 

 the two polar regions. I conceive that in a spheroid con- 

 structed of partially elastic materi.rls, the effect of such a stric- 

 ture will cause, besides a sensible diminution of the whole 

 periphery of the sphere, a lateral thrust at right angles to the 

 pressure applied, and thus only can I account for it. This 

 would, if I am not mistaken, have another effect, and this a very 

 important one ; it would induce magnetism in the earth, and that 

 magnetism would have its poles in the regions of upheaval, and 

 this is in fact so. The magnetic poles are strictly, so ilir as our 

 evidence goes, in the very foci of upheaval of the circumpolar 

 regions. This correlation of terrestrial magnetism with the force 

 that is causing a tension about the earth's equator, if sustained 

 would surely go far to explain that crux ot physical science 

 referred to by Sir William Thomson in his address to the 

 British Association at Edinburgh, namely, the cause of the earth's 

 magnetism; but my letter has already outgrown reasonable limits, 

 and I must ask you to allow me to continue the subject in 

 another. IIenrv II. Howorth 



Derby House, Eccles, Jan. 2 



Vivisection 



It has been suggested that the study of Huxley's " Ele- 

 mentary Physiology" is likely to make children indulge in cruelty. 

 Allow me to give the experience of the father of five boys on the 

 subject. 



Those old enough to be taught from that book are so ; 

 and have attended the professor's lectures and seen some of his 

 experiments. The impression left on their minds, from the 

 reverent and touching treatment of the subject by the able pro- 

 fessor, has led to an improved and exalted respect for the rights 

 and life of the meanest thing that crawls. 



Although these boys are now at what may be called the " pre- 

 datory age," the interest and respect they evince for animal 

 life is mainly to be attributed to the beautiful and refining lec- 

 tures of the worthy and humane Huxley. 



G. W. Cooke 



London, E.G., Jan. 5 



Moraines 



Mr. Frv, writing in Nature (vol. ix. p. 103), says that "a 

 glacier which has retreated from its terminal moraine is always 

 the source of a stream of water, and this stream always cuts 

 through the terminal moraine." He infers from this that a lake 

 cannot be formed by a moraine damming up a valley. 



I can assure him that this is a fact which at least admits of ex- 

 ceptions. The valley of the Kander in the Bernese Alps is, in 

 its upper part at least, full of the moraines of extinct glaciers, 

 now mostly overgrown with pine forest. One of these dams up 

 a side valley and forms the beautiful Ocschinen Lake. The lake 

 is fed from the glaciers of the B!um'.is Alp, and its water is conse- 

 quently muddy. Except in most unusual floods, it has no outlet 

 above ground, but the side of the dam farthest from the lake is 

 one mass of springs of w.ater .is clear as the celebrated sti'eams of 

 Lauterbrunnen, which are evidently fed by the water of the lake 

 filtering through the dam. The dam, being a moraine, is of 

 porous material. Joseph John Murphy 



Old Forge, Dunmurry, Dec. 24, 1873 



