NATURE 



505 



THURSDAY, SEPTEJ.IBER 30, 18S0 



LANDSLIPS 



FEW disasters impress the mind so vividly with human 

 helplessness as those that arise from disturbance of 

 the sohd ground beneath our feet. The most devastating 

 hurricane can in some measure be foreseen and provided 

 against. Skill and foresight continually do battle with 

 the fury of the w-aves, and prove on the whole victorious. 

 We are so familiar with the restlessness of air and ocean 

 that the havoc wrought by these elemental powers does 

 not carry with it the sense of aught unusual or against 

 which we may not hope successfully to contend. But to 

 I find that the earth beneath us, to which we have, 

 [ consciously or not, trusted as the only stable feature in 

 our landscape, gives way in a moment of unsuspicious 

 j calm, that the everlasting hills are themselves perishable 

 like everything else, that ruin and death may in an 

 instant overwhelm alike scenes of sylvan quiet and of 

 active human industry, brings to the mind that practically 

 experiences the sensation a horror to which there is 

 hardly any parallel in the long list of calamities that thin 

 the ranks of mankind. 



Terrestrial commotions of this nature are obviously 

 divisible into tw-o classes. There are first tremors, of 

 which the far-reaching and destructive earthquake is the 

 most signal example. Much has been said and written 

 about the cause of earthquakes, but we are still far from 

 a satisfactory solution of the problem. Probably more 

 causes than one conspire at different times to produce the 

 impulse which sets the earth-wave in motion. But what- 

 ever may be their nurture and origin, these operations 

 belong to that large class in which the internal tempe- 

 rature of the planet, with the results of its reactions and 

 its diminution is the chief factor. In the second place 

 come the disturbances arising from the working of the 

 different agents which are set in motion by the direct 

 influence of the sun. Among these the operations of 

 running water are by far the most important. 



There can be no doubt that it is in this second class of 

 phenomena that the melancholy catastrophe at Naini 

 Tal must be placed. In various ways the action of 

 running water disturbs the equilibrium of large masses 

 of rock at the surface. The frequent undermining of 

 its banks by a rivulet or river, with the consequent fall 

 of slices of earth or rock into the stream, is a familiar 

 illustration. The dislocation and dislodgment of portions 

 of cliffs by the wedging influence of frozen water is 

 another common example. But the most extensive 

 changes of this kind arise from the influence of water 

 underneath the surface, where the geological structure of 

 the ground happens to be favourable. Trickling through 

 the pores, joints, and fissures of rocks, rain or melted 

 snow makes underground channels for itself. In the 

 course of its progress it sometimes dissolves away large 

 quantities of stone, or loosens and carries away in 

 mechanical suspension the minuter particles of rocks. 

 When this abstraction of materials takes place along a 

 subterranean slope, the lower end of which comes out on 

 the side or bottom of a valley, the effect is to enfeeble 

 the support of the mass of rock resting upon the slope. 

 Vol. XXII. — No. 570 



Eventually this overlying mass may by gravitation break 

 off from its floor and slide down into the valley below. 

 Or should an open porous layer form the platform on 

 which the side of the valley or cliff rests, copious rain 

 may so saturate it as to loosen the cohesion of the super- 

 incumbent mass, which, when its weight overcomes that 

 cohesion, is launched forward into the low ground below it. 

 The saturated stratum may be compared to the grease 

 put upon the beams on which a ship is launched from the 

 building-yard. The moisture lubricates the bottom of the 

 overlying rock and allows it to slide down. Such " land- 

 shps," as they are termed, are of common occurrence in 

 countries with a copious rainfall, where the ground is 

 uneven and rests on rocks containing easily permeable 

 strata intercalated among others of a more impervious 

 kind. The dislodged mass rushes down with irresistible 

 impetus, breaking up into tumultuous piles of ruin, under 

 which woods, meadows, gardens, fields, houses, and their 

 inhabitants are almost instantly overwhelmed. 



Every summer tourist whose wanderings have led him 

 round the coasts of these islands is doubtless familiar 

 with tracts of landslip, some comparatively recent, others 

 so ancient as to go back far beyond the times of tradition 

 or of local history. He will remember how in localities 

 where the scenery would otherwise be of the tamest kind, 

 the ground has been thrown into picturesque knolls and 

 crags, with Uttle glens and valleys winding through them, 

 how the gathered drainage tumbles over miniature falls 

 or collects into diminutive tarns which, in all save size; 

 remind him of mountain lakes, and how over the whole 

 scene the kindly hand of nature has spread her verdure, 

 healing the scars of the original catastrophe by hanging 

 festoons of ferns and mosses over the shattered rock^ 

 smoothing and carpeting with velvet turf the once naked 

 floors of loose detritus, and scattering over dingle and 

 den a pleasant shade of copsewood. The under cliffs of the 

 Isle of Wight and other parts of the south coast, the clay 

 chffs of Sheppey and Yorkshire, the northern sea-front of 

 the Antrim coast, the shores of Skye and adjacent islands 

 of the Inner Hebrides furnish admirable illustrations of 

 every stage in this history, from the raw wound of last 

 year to the fairy-like scenery which conceals the landslips 

 of remote centuries. 



Fortunately in Britain we have no harrowing chronicle 

 of human death connected with the story of our landslips. 

 Yet these have not been without occasional loss of life, 

 and sometimes considerable destruction of property. It 

 has been estimated that the coast of Yorkshire between 

 Spurn Point and Flamborough Head loses about i\ 

 yards annually, slice after slice of the clay cliff slipping 

 down to the beach, where it is readily attacked and 

 removed by the waves. The clay cliffs of the Isle of 

 Sheppey suffer similar rapid removal, while the chalk 

 cliffs of the Isle of Thanet have had a yearly loss of three 

 feet. From fields that were ploughed and sown with 

 corn in spring segments slip down, so that in these 

 detached portions the crop may be seen ripening half 

 way down the cliff. In the w-ell-known landslip of 

 December, 1839, near Lyine Regis, a strip of chalk cliff 

 three-quarters of a mile long, 240 feet broad, and from 

 100 to 1 50 feet high was undermined by the descent of 

 continuous heavy rain and the saturation of a thick 

 deposit of loose sand underneath. It consequently slid 



