10 



considerable proportion of linie being deposited, a great portion of the lime 

 subsequently separating itself from the semi-tluid mass. 



The conditions under which the otlier class were deposited must have been 

 widely different. Sometimes the beds may be traced for a considerable distance, 

 but generally they vary much in thickness and structure often even in a few 

 yards, and this variability seems to be in proportion to their approach to a 

 conglomerate form. They are often stratified, and fiequently lenticular masses 

 of sandstone are intercalated in them in a way which only seems explicable by 

 currents acting in comparatively shallow water. The coarseness of the materials 

 often included favours the same view. They are not such as could be held in 

 suspension and deposited in deep water at a distance from shore. Many of them 

 evidently contain rolled pebbles derived from pre-e.xisting rocks, and in some of 

 the beds I have found pebbles several inches in diameter, formed of an exceed- 

 ingly fine-grained limestone, not referrible to any known pre-existing rook. 

 The source of these pebbles is a fertile subject for speculation, and if organic 

 remains could be discovered in them it might throw much light on geological 

 records. 



These deposits are called Cornstones, a name originating, I believe, in this 

 locality, and one which has been employed so loosely as to give rise to a good 

 deal of confusion. It is used not only to describe the deposits themselves, but 

 that division of the Old Red Sandstone in which they are believed especially to 

 occur. With regard to the distribution of the deposits themselves they are 

 traceable to within a very few feet of the tilestones or passage beds at the bottom 

 of the system, and so far as I have been able to examine the upper part of the 

 fonnatiou in our mountains, I have found in greater or less proportion both 

 forms of deposit which I have described, up to within perhaps 1,000 feet below 

 the carboniferous limestone. 



By the Cornstone division, or series of the Old Red Sandstone, is usually 

 meant the lower division, though, as Murchison observes, the middle division 

 contains the greatest quantity of these deposits. It must be borne in mind, 

 however, that these divisions are by no means of a definite kind. If a definite 

 division is possible we must probably wait for it until the various parts of the 

 Devonian system are better understood. 



After what I have said as to the distribution of the Cornstones, it will 

 be evident that their palaeontology is almost equivalent to that of the entire Old 

 Red system, as the fossil remains are generally found either in the calcareous 

 beds, or in their immediate vicinity. I have never found anything in the 

 nodular deposits. You are probably aware that in some parts of the Old Red 

 Sandstone of Scotland, the caloareovis nodules yield a rich harvest of fossils, the 

 organism apparently acting as a nucleus round which the lime was deposited. 

 I am not aware that anything of the kind has been observed in this district, 

 though it would be well to make repeated and careful examination of the nodules. 

 Our scanty fauna is found in the conglomerated Cornstones, and these are not 



