106 P. Mdenair $ J. Rekl—On the Old Bed of Scotland. 



one kilometre in 10 seconds : total about 40 seconds. If to this we 

 add 50 per cent, for the various retarding resistances, the estimated 

 time within which the ice-avalanche did its work of destruction is 

 not more than one minute. 



It is a singular coincidence that a similar ice-avalanche occurred 

 at the same spot over 100 years ago, on the 18th August, 17^2. 

 As in the year 1895, so also in the year 1782, great heat prevailed 

 in the months of June, July, and August, and the rupture of the 

 glacier was therefore in both cases due essentially to meteorological 

 causes. 1 The present disaster falls short of the rock-fall of Elm (in 

 the Glarus Alps) which occurred in 1881 on the same day, the 11th 

 September, and caused the loss of 114 lives and 79 buildings, the 

 volume of the debris being about double that of the Altels ice- 

 avalanche. It also falls short of the ice-avalanche which destroyed 

 the village of Eanda in the Visp valley in the year 1819, the volume 

 of" glacier debris being in that case nearly four times that of the 

 Altels avalanche. Still, the magnitude of the latter, and the scale 

 on which Nature works in the Alps, may be gathered from the fact 

 that the detached glacier swept down a declivity whose vertical 

 height is thirteen times that of St. Paul's Cathedral (365 feet) ; that 

 it was then hurled up to a height four times the elevation of that 

 building ; and that the volume of its debris under which the Alpine 

 pasture is now buried, would suffice to cover to a depth of three 

 feet the combined area (about 1000 acres) of Regent's Park, Hyde 

 Park, and Kensington Gardens. 



III. — On the Physical Conditions under which the Old Red 

 Sandstone of Scotland was Deposited. 



B}- Peter Macnair and James Eeid. 



I. Introduction. 



THE physical conditions under which the Old Red Sandstone of 

 Scotland was formed is a subject that has long occupied the 

 attention of many of our leading geologists, from the time of Hugh 

 Miller and Sir Roderick Murchison down to those of the present day. 

 It has been variously regarded as of fresh-water and marine origin, 

 as having been thrown down in lakes and in the open sea, or in 

 inlets of the latter. But as yet the whole matter seems to remain 

 an open question, which the unique physical and palasontological 

 elements of the formation make difficult of solution. 



This contribution to the controversy does not attempt to untie the 

 Gordian knot, but is simply to show that much of the evidence 

 freely assumed to be in favour of a fresh-water and lake origin for 

 these deposits may or may not admit of proof, while on the other 



1 The precise date of the avalanche of 1782 is fixed by a public document, which 

 was discovered through the efforts of Prof. Forel, of Morges, in the archives of 

 Loueche, and enumerates the loss of life and property sustained on that occasion : 

 " per terribilem et stupendam de summitate rnoutis prolapsam glaciei quantitatem." 

 On that occasion four men, who were crossing the Spitalmatte on their way home, 

 and ninety cattle, were killed. 



