68 ANNALS OF SCOTTISH NATURAL HISTORY 



for a short distance. He considers that in most cases a 

 channel ten miles in width would prove an effective barrier 

 to most mammals. This would certainly be the case as to 

 most of the smaller species of cats, as well as to those 

 animals upon which their existence depended. The lemmings, 

 for instance, described by Wallace as migrating in their 

 hundreds of thousands, cross rivers and lakes with impunity, 

 but nearly all perish from the salt water if they attempt to 

 cross an arm of the sea. 



Assuming that these wide estuaries and arms of the 

 sea were the chief obstacles to migration, the next point for 

 consideration is : When were they sufficiently obliterated to 

 allow of a free and safe passage ? According to Sir Charles 

 Lyell (" Antiquity of Man," p. 55), the conversion of the sea 

 into land has always been considered by antiquaries to have 

 been caused by the silting up of the estuaries, both in respect 

 to the Solway and the Forth. " Thus Horsley insists on the 

 difficulty of explaining the position of certain Roman stations 

 on the Solway, the Forth, and the Clyde, without assuming that 

 the sea had been excluded from certain areas which it had 

 formerly occupied." Lyell goes on to say that, " on a review 

 of the whole evidence, geological and archaeological, afforded 

 by the Scottish coast-line, we may conclude that the last 

 upheaval of twenty-five feet took place, not only since 

 the first human population settled in the island, but long 

 after metallic implements had come into use ; and there 

 seems even a strong presumption in favour of the opinion 

 that the date of elevation may have been subsequent to the 

 Roman period." But this rise of twenty-five feet was only 

 the last stage of a long antecedent process of elevation ; and 

 during that earlier period the Wild Cat and the smaller rodents 

 had probably the means of migrating afforded to them by 

 the drying up of some portion of these estuaries. 



As the bones of the cat have only been found in the latest 

 deposits of the Quaternary series, namely in the shell marl 

 deposits of some of the Forfarshire lakes, which have been 

 drained in order to use the marl for agricultural purposes, 

 under what circumstances did these bones get there ? 



Lyell remarks that these marls often consist entirely 

 of an aggregate of shells of the genera Limnaea, Planorbis, 



