266 



HARDWICKE'S SCIENCE-GOSSIP. 



|Dec. 1, 1870. 



together, and thus'producing a hard rock. When 

 this chemical agent has been equally dispersed 

 through the sandy mass, you have the thick-bedded 

 sandstone, or "free-stone." When it was intermit- 

 tent in its action, or unduly mixed up, or occasion- 

 ally alternated with something else, then the sand- 

 stone becomes " flag-stones " of greater or less 

 thickness. 



Sometimes you will see a mass of red sandstone 

 more or less mottled. This has been caused, in- 

 most instances, by patches of vegetable matter — 

 old world fucoids or something of that sort, — which 

 decomposed, and whose chemical changes combined 

 with the iron, and locally prevented its colouring 

 effect. 



Gf course it will be evident that our hardness 

 or softness greatly depends on the percentage of 

 cementing material, or to the different circum- 

 stances under which we were formed. I have no 

 doubt that, when the chemical changes above men- 

 tioned were going on through an immense thickness 

 of accumulated sand, the hardening process was 

 greatly assisted by the pressure of the overlying 

 volume of sea-water. 



The epoch to which I belong is sometimes called 

 the " Old lied Sandstone," and, occasionally, the 

 "Devonian." The former term is given to our 

 formation to distinguish us from the "New Red 

 Sandstone," overlying the coal-measures ; whilst 

 the latter 'name is of local origin, and indicates that 

 the system is largely developed in the lovely county 

 of Devon. Indeed, that sunny land owes no little 

 of its physical attractions to the various minera- 

 logical structure of the rocks of our formation. 

 Perhaps I can boast of the fact that there are few 

 other formations which have such a world-wide 

 extent as that to which I belong. In the United 

 States it extends over an area nearly as large as 

 Europe, there being one continuous coral reef in- 

 cluded in it, which covers an area of nearly half a 

 million of square miles. In Canada there is also a 

 great extension of this formation, whilst in Soutli 

 Africa its area is greater still. In Russia one sub- 

 division is much greater than the whole of England, 

 and there is a large extension of beds of similar age 

 in Asia Minor, as well as in Australia. 



The original name of " Old Red Sandstone," — 

 given to the formation of which I am an humble 

 part, was conferred upon the thick beds found 

 developed in Herefordshire, Worcestershire, Shrop- 

 shire, and South Wales, as well as others supposed 

 to be of similar age in Scotland. In the former 

 localities they attain their greatest thickness, 

 which is between eight and ten thousand feet. 

 There, geologists have divided the series into four 

 divisions, of which the lowest may be said to blend 

 with the underlying Silurian formation, and the 

 uppermost with the succeeding Carboniferous. In 

 Scotland the beds are not so thick, their greatest 



vertical accumulation amounting to about four 

 thousand feet. It would seem, therefore, as if the 

 material which formed these rocks came from the 

 south-west, thinning out in anorth-easterly direction. 

 In Devonshire, as well as in Ireland, there are two 

 series of strata included in the same formation, 

 which seem to have had quite a different origin. 

 The former indicate a deep sea in which coral reefs 

 abounded, and the latter tells us plainly of a large 

 continent which existed towards the end of this 

 epoch, on which there stood freshwater lakes as 

 extensive as those of North America. Doubtless 

 it was the same continent whose rivers contributed 

 no little of the sand and mud which, when strewn 

 on the sea-bottom, formed the sandstones of which 

 I am part. 



How shall. I tell of the strange sights which I 

 beheld when quietly lying on the ocean-floor ! The 

 sea-water had the same specific gravity it has now, 

 and the constitution of the atmosphere was similarly 

 formed. It is an error to suppose, as some have 

 done, that there was mixed a large percentage of 

 carbonic acid in the air before the Carboniferous 

 epoch, and that this was absorbed, and the atmo- 

 sphere cleared and rendered fit for animal life at the 

 same time. The theory is ingenious, but there is 

 not the slightest ground for believing it has any 

 foundation in truth. Occasionally the sea-water 

 became turbid and red, owing to larger quantities 

 than usual of the refuse of igneous and metamor- 

 phic rocks being carried down by the rivers. As is 

 well known, these contain large quantities of iron, 

 which are easily decomposed, and enter into new 

 combinations as oxides ; whence my colour and also 

 my cementing agent. The sea-bottom was covered 

 with groves of fuci, or sea- weeds, in which a large 

 crustacean, bearing some resemblance in its huge 

 claws to the modern lobster, lived and left its 

 spawn. The latter is actually found fossilized in 

 our sandstones, and bears some resemblance to a 

 flattened blackberry. Among geologists, I am told, 

 it goes by the name of Parkia, whilst the huge 

 lobster which left it, and which was at least six or 

 seven feet long, rejoices in the name of Pterygoids. 

 Several species of this common form are met with 

 in Scotland, as well as in England. 



But by far the commonest creatures which en- 

 joyed life in the sea of my birth were the fishes. 

 Indeed, my epoch has been justly called "the age 

 of fish." In many places they swarmed in shoals. 

 Most of them belonged to an order of which there 

 are very few now living, termed the Ganoid, on 

 account of their being covered with a series of 

 oval or rhomboidal bony plates, instead of scales. 

 These bony plates had an exterior varnish ; whence 

 their name. At present, I am told, there are 

 several species living in the rivers of North Africa, 

 and others enjoying life in the lakes and rivers of 

 North America. But out of nine thousand species 



