Cii. XV.] 



RECENT RAIN-PRINTS. 



335 



• 





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> 













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: 



middle of a rain -mark, having been formed subsequently. 

 Sometimes the worms have dived beneath the surface, and 

 then reappeared. All these appearances, both of rain-prints 

 and worm-tracks, are of great geological interest, as their 

 exact counterparts are seen in rocks of various ages even in 

 formations of very high antiquity* Small cavities, often 

 corresponding in size to those produced by rain, are also caused 

 by air-bubbles rising up through sand or mud ; but these 

 differ in character from rain-prints, being usually deeper than 

 they are wide, and having their sides steeper. These, indeed, 

 are occasionally vertical, or overarching, the opening at th< 

 top being narrower than the pit below. In their mode, also, 

 of mutual interference they are unlike rain-prints.f 



In consequence of the effects of mountains 

 currents of moist air, and causing the condensation of aqueous 

 vapour in the manner above described (page 329) it follows 



in cooling 



that in e^ery country, as a general rule, the more elevated 

 regions become perpetual reservoirs of water, which descends 

 and irrigates the lower valleys and plains. The largest quan- 

 tity of water is first carried to the highest region, and made 

 to descend by steep declivities towards the sea ; so that it ac- 

 quires superior velocity, and removes more soil, than it would 

 do if the rain had been distributed over the plains and moun- 

 tains equally in proportion to their relative areas. The water 

 is also made by these means to pass over the greatest dis- 

 tances before it can regain the sea. 



Earth-pyramids or stone-capped pillars of Botzen in the 

 Tyrol.— 



of rain can be studied separately or as distinct from those of 

 running water. There are, however, several cases in the Alps, 

 and especially in the Tyrol near Botzen, which present a 

 marked exception to this rule, where columns of indurated 

 mud, varying in height from twenty to a hundred feet, and 

 usually capped by a single stone, have been separated by rain 

 from the terrace of which they once formed a part, and now 

 stand at various levels on the steep slopes boundino* narrow 



It is not often that the effects of the denuding action 





* See Elements of Geology, Index Quart. Journ. Geol. Soc. 1851, vol. vii 



Barn-prints. 



t See Lyell on recent and fossil rains. 



p. 239 



