Royal Institution of Great Britain. 211 



by the river as it gradually deepened its channel and extended its 

 lateral curvature. 



The valley of the Meuse near Givet, offers, through a great di- 

 stance, a number of similar windings, and the same thing is seen at 

 intervals in many of the other rivers of that country. Parts of the 

 Seine below Paris, and the valley of the Wye between Hereford 

 and Chepstow, are examples nearer home. 



Valleys which like these twist about in the same regular curves 

 as the channel of a brook meandering through a meadow, can, ac- 

 cording to the author, only be accounted for by the slow and long- 

 continued erosion of the streams that still flow in them, increased 

 at intervals by wintry floods. To attribute them to a transient and 

 tremendous rush of water in the main direction of the valley, is in 

 his opinion impossible. He contends that whilst these valleys were 

 slowly excavated, other rivers could not have been idle during the 

 same protracted period ; but will have produced likewise an amount 

 of excavation proportioned to their volume and velocity, and the 

 nature of the rocks they flowed over. In the examples quoted, 

 the rocks are mostly hard transition strata, yet the valleys are wide 

 and deep. Where softer strata, as sands, clays, and marls, were 

 the materials worked upon, the valleys excavated maybe expected, 

 as they are found to be, far wider in proportion to the volume of 

 water flowing through them. The comparative softness of the ma- 

 terials also, by accelerating the lateral erosion of the stream, will 

 have multiplied the shiftings of its channel, and reduced their sum 

 with greater certainty to one average direction. Hence the deeply 

 sinuous valleys are only found penetrating the more solid rock 

 formations. The author thinks that a certain subdued velocity in 

 the stream is also necessary to produce this result; and, therefore, 

 in mountainous districts, where the torrents and rivers are most 

 rapid, their course is nearly straight; thus confirming the author's 

 opinion, that extreme curvature of channel can only be produced 

 by a slow and comparatively tranquil process of excavation. 



FRIDAY-EVENING PROCEEDINGS AT THE ROYAL INSTITUTION 

 OF GREAT BRITAIN. 



Jan. 22.— On this evening Mr. Faraday gave an illustrated 

 account of the endeavours lately niade^by the Chevalier Aldini to 

 guard firemen from the effects of flames. He first demonstrated the 

 general principles of flames, then adverted to the peculiar circum- 

 stances and conditions of the flames which arise in the combustion of 

 dwellings, their lateral and undulatory action, &c. and finally illus- 

 trated M. Aldini's propositions, by exhibiting the apparatus of that 

 philosopher (who is at this moment in London), and showed the 

 defence it afforded by exposing a man, guarded by its means, to the 

 powerful flame of portable gas. The defensive armour consists of a 

 double clothing of asbestos cloth and wire gauze, and its defensive 

 power appeared to be very great. Some magnificent specimens of 

 2 E 2 asbestus 



