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(ii. XV.] 



EECENT RAIN-PRINTS 



OOQ 



o o o 



Recent rain-prints.— When examining, in 1842, the exten- 



sive mi' 



Nov 



on the borders of the Bay of Fundy, I observed not only 

 the foot-prints of birds which had recently passed over the 

 mud, bnt also very distinct impressions of rain-drops. A 

 peculiar combination of circumstances renders these mud-flats 

 admirably fitted to receive and retain any markings which 

 may happen to be made on their surface. The sediment 

 with which the waters are charged is extremely fine, being 

 derived from the destruction of cliffs of red sandstone and 

 shale, and as the tides rise fifty feet and upwards, large areas 

 are laid dry for nearly a fortnight between the spring and neap 



In this interval the mud is baked in summer by a hot 

 sun, so that it solidifies and becomes traversed by cracks, 

 caused by shrinkage. Portions of the hardened mud may 

 then be taken up and removed without injury ; and a cross 



tide 



numer 



tides, each layer being usually very thin, sometimes 

 one-tenth of an inch thick. When a shower of rain 



the 



highest portion of 



the mud-covered flat is usually 



uncovered by the tide near the water's edge is too 



too hard to receive any impressions; while that recently 



soft. 



Between these areas a zone occurs, almost as smooth and 

 even as a looking-glass, on which every drop forms a, 



cavity of 



circular or 



oval form, and, if the shower be 



transient, these pits retain their shape permanently, being 

 dried by the sun, and being then too firm to be effaced by 

 the action of the succeeding tide, which deposits upon them 

 a new layer of mud. Hence we often find, on splitting 

 open a slab an inch or more thick, on the upper surface 

 of which the marks of recent rain occur, that an inferior 

 layer, deposited during some previous rise of the tide, exhibits 

 on its under side perfect casts of rain-prints, which stand out 

 in relief, the moulds of the same being seen on the layer 

 below. But in some cases, especially in the more sandy layers, 

 the markings have been somewhat blunted by the tide, and 

 by several rain-prints having been joined into one by a repe- 

 tition of drops falling on the same spot; in which case the 

 casts present a very irregular and blistered appearance. 



