TRAXS ACTIONS OF SECTION C. 879 



pass through a series of uniform climates at sea level, gradually decreasing in 

 temperature and terminating in an ice age ; that this age must be succeeded by a 

 zonal distribution of climates gradually increasing in temperature and extent. 



The conclusions reached -were : (1) that in the case of the earth zonal distri- 

 bution of climates was inaugurated at the culmination of the ice age, and i» 

 gradually increasing in temperature and extent by the trapping of solar energy in 

 the lower regions of the atmosphere, and that this rise has a moderate limit ; (2) 

 that the ice age was unique and due to the physical properties of water and air, 

 and to the difference in specific heat of land and water ; and (3) that prior to the 

 ice age local formation of glaciers could occur at any latitude and period. 



It was pointed out that Jupiter is apparently in a condition through which 

 the earth has passed ; and that Mars is apparently in a condition towards which 

 present climatic evolution is tending. 



3. On the Sub-oceanic Physical Features of the North Atlantic. 

 By Professor Edward Hull, LL.D., F.R.S., F.G.S. 



The remarkable results arrived at by Professor Spencer and other American 

 geologists regarding the sub-oceanic physical features of the Atlantic seaboard 

 and the West Indian Islands induced the author to undertake a similar series of 

 investigations along the eastern coast of the North Atlantic by the aid of 

 soundings of the Admiralty Charts. These investigations extend from the neighbour- 

 hood of Rockall (lat. 67° 30' N.) as far south as Cape St, Vincent, a distance of 

 about 1,500 English miles, with a coast-line of about 2,000 miles, and were 

 determined by tracing a series of contour, or isobathic, Imes on the charts. The 

 contours chiefly employed were those of 100, 250, 500, 750, 1,000, 1,200, and 

 1,600 fathoms. The features determined were as follows : — 



1 . The British and Continental platform, long since known under the name 

 of ' the 100-fathom platform,' extends for variable distances outwards to the 

 lOO-fatliom contour ; but the author has found that this contour by no means 

 represents the pliysical limit of the platform, as the seaward margin is formed by 

 the abrupt descent of the sea-floor at depths varying, according to the position, 

 from 100 fathoms at the Vidal Bank off" the coast of Scotland, to the 250-fathom 

 contour off the coast of Ireland in lat. 53° N. Off the coast of Spain the platform 

 generally coincides with the 200-fathom contour. The platform thus defined is 

 frequently indented by deep bays and traversed by old river channels, one of the 

 most remarkable of which is ' the Hurd Deep ' in the English Channel, traceable for 

 70 miles on the chart, and descending to a depth of 60 fathoms, or about 25 fathoms 

 below the general level of the platform at this part. The platform all through has a 

 floor of gravel, sand, and clay, with shells ; and off the Enghsh coast has been 

 described by Mr. Godwin-Austen in his paper on ' The Valley of the English 

 Channel.' ' 



2. The second important feature indicated by the isobathic contours may be 

 designated ' The Grand Escarpment,' along which the platform above described 

 breaks oft' seawards. This escarpment is traceable from off Rockall and the Outer 

 Hebrides, between which there is a deep bay, southwards to Cape St. Vincent. It 

 follows the coast of the Bay of Biscay, at distances varying from 100 miles off the 

 western coast to 20 or 30 miles off the southern coast. This great escarpment, about 

 2,000 miles long from north to south, has nothing comparable with it as regards 

 magnitude in the British Isles and Europe. It is limited upwards by the 100 to 250 

 fathom contours, and downwards by those of 1,200 to 1,500 fathoms, thus giving 

 an altitude (regarded from the point of view of having been once a land feature) 

 of over 6,000 to 7,000 feet, according to locality. The base of the escarpment can 

 be clearly determined at several points, as, for example, north of the Porcupine 

 Bank (lat. 64° N.) and at the embouchure of the old caiion of the river Adour, 



' Quart. Journ. Gcol. Soc, vol. vi. (1849). 



