596 Proceedings of the Royal Society 
the subject recurred to me. In order to bring as much light to 
bear upon it as possible, I greatly extended the number of analyses 
which I undertook ; and, as hearing upon it, I have now analysed 
20 specimens of augite and its allomorphs, 15 of hornblende, and 
21 of the products of the alteration of these two substances. 
Founding upon the information gained thereby, I work out 
chemically the various steps and stages of the transmutation, — which 
transmutation will be shown and seen to be the formation of 
serpentine. 
2. On the Old Red Sandstone of Western Europe. By 
Professor Geikie, F.R.S. 
In a historical introduction the author gives an outline of the 
progress of research into the history of the Old Red Sandstone of the 
British area. This system is at present regarded as composed of three 
sub-divisions, Lower, Middle, and Upper, each characterised by a dis- 
tinct suite of organic remains. From the absence of unequivocally 
marine fossils, and from lithological characters, it has been inferred 
by Mr Godwin Austin, Professor Ramsay, Professor Rupert Jones, 
as well as other observers, and is now very generally admitted, 
that the Old Red Sandstone, as distinguished from the “Devonian” 
rocks, probably originated in inland sheets of water. The object of 
the present memoir was to endeavour to trace out in that geological 
system of deposits the changes of physical geography which took 
place over Western Europe during the interval between the close 
of the Upper Silurian and the beginning of the Carboniferous 
period. 
After a sketch of the probable conditions of the region previous 
to the commencement of the Old Red Sandstone, the author pro- 
ceeds to show how the shallowing Silurian sea was converted here 
and there into salinas or inland seas, by a series of subterranean 
movements, which have left their indelible traces upon the upturned 
Silurian rocks. He divides his memoir into two parts, the first 
dealing with the Lower and the second with the Upper Old Red 
Sandstone. The present paper deals only with a portion of the first 
of these sections. It traces out the limits of the different basins in 
which the Old Red Sandstone of the British islands were deposited, 
