434 Fish and Drought 



date of the death of the crowd of fishes which voluntarily 

 entombed itself in the mud before desiccation was complete, 

 and the date at which the stratum of mud and remains so 

 produced would be entitled to rank as a geological formation. 

 I do not know if there are any adequate data for arriving at 

 a trustworthy estimation of the probable length of this interval. 

 It is quite distinct from what is understood as the age of the 

 geological formation. 



The barren districts of sandy and marly matter at the 

 bottom of the ditch would, after the lapse of the same, or 

 perhaps a shorter, interval furnish perfectly unfossiliferous 

 strata, which would suggest to the geologist of later date that 

 the water basin in which it had been laid down had been 

 singularly devoid of aquatic life. Yet, in a sense, it would not 

 be inaccurate to say that the water basin in which the muddy 

 strata holding the crowded fish remains had been "laid down" 

 teemed with life, and that the barren strata had, in the same 

 sense, been "laid down" in water devoid of aquatic life; 

 although the two bodies of water formed one continuous sheet 

 of very restricted dimensions. It would seem, therefore, that a 

 material barrier is not necessary to separate even a small body of 

 water into two basins and to maintain them distinct, the one of 

 which may be full of life and the other practically barren. 



There is an important point, which should not be missed, 

 in the similarity between what took place this summer at 

 Marchais and what may have taken place in Caithness or 

 Orkney in the Old Red Sandstone period. The fishes which 

 buried themselves in such numbers in the mud this summer, 

 though they were fortunately released, were in the strictest 

 sense contemporaries, and were all buried in the mud within 

 a few days of each other. Moreover, in ordinary circum- 

 stances, at least in summer, the mud is untenanted. If the 

 fish were to migrate into the barren waters covering the marly 

 bottom, and their return were barred while the water over the 

 mud evaporated and the secular drought set in, this same 

 mud-bed would be met with in later ages as an unfossiliferous 

 stratum. So that the fossil fishes which are found in these strata 

 must be held to have gone into occupation only when the signal, 



