observed on the Roclis on the Shores of Greece. 343 



and afterwards the rain-waters and dews produce grooves, by 

 flowing according to the direction of the greater declivity, and 

 carrying along with them the disunited parts. 



The phenomenon is thus explained in a manner altogether 

 mechanical. Yet it might be possible that the waters of the sea 

 might have had a chemical action upon these limestone rocks, 

 which are almost all more or less mixed with magnesia, and 

 doubtless deposited in the waters under very different circum- 

 stances. 



The Grey Zone. 



When we ascend the upper part of this zone, we observe that 

 the bottom of the cavities begin to be covered with a greyish 

 lichen, with little scattered black globules, resembhng grains of 

 powder ; and if we break the rock, we very often see, at about 

 a millimetre under the surface, an embroidering of beautiful 

 emerald-green, which surprises us the more as between it and 

 the lichen the rock is not altered. One might be tempted to 

 see, in these circumstances, the proof of a destructive action, 

 which the lichens would exert on the limestones ; but there is 

 nothing of the kind. A more attentive observation shews that 

 this green matter occupies only fissures invisible to the naked 

 eye, where it ceases at a certain depth. Thus vegetation here 

 exerts a conservative action ; it opposes the destructive action of 

 the aura marithna, and terminates by vanquishing it ; quickly 

 every trace of erosion ceases, and the rock, still deprived of other 

 vegetation, is covered with a uniform gi-ey tint. 



I do not believe, after what has just been stated, it can be 

 supposed that the corrosion of these littoral rocks commenced at 

 an epoch anterior to ours ; from those times, " when, accord- 

 ing to some geologists, acid rains washed the surface of the 

 rocks, or torrents of acid water rushed from the bosom of the 

 earth, dissolved every thing in its passage, gave rise to diluvium, 

 and scooped out valleys;"" — opinions which appear to me to be- 

 long rather to the geology of the eighteenth than the nineteenth 

 century. Besides, the examination of historical monuments 

 would refute this objection. (I might cite many of these, but 

 these details will be placed with greater propriety in a work 

 upon the Morca.) A great number of monuments, of high an- 

 tiquity, of Cyclopean or Hellenic construction, situated within 



