in Regard to Wind Pressures. 45 



point more than 7 lbs., thus showing the designer, in the 

 clearest way, the proper thickness of brickwork to be used, 

 and at what points to change from one thickness to another. 

 The consideration of the wind pressure in connection 

 with roofs and bridges must be left for treatment in another 

 paper. 



Aet. IV. — Evidences of a Glacial Epoch from Kerguelen's 

 Land, being Cor)ir)%ents upon the " Challenger' Reports. 



By Mr. G. S. Griffiths. 



[Read 13th May, 1886.] 



The occasion of adding to our library two volumes which 

 summarise the labours of the "Challenger" expedition, affords 

 me an opportunity of describing some discoveries in 

 Kerguelen's Land which tend to throw some more light upon 

 the nature of the climate of this hemisphere in the past. 



Kerguelen's Land is a small island placed upon an isolated 

 submarine plateau about 450 miles long and 250 miles wide, 

 situated in 49 deg. S., 68 deg. W. Its coast-line is broken on 

 every side by deep sounds, and two ranges of comparatively 

 lofty mountains divide the limited territory between them. 

 The western range has a mean height of about 3400 feet, 

 and an extreme one of 6120 feet. The eastern system has a 

 mean of 3000 feet. The mountains appear to be a series of 

 extinct volcanoes, but the west coast has one still active, 

 and it is surrounded by hot- water springs, petroleum springs, 

 and mineral pitch deposits, all phenomena characteristic of 

 the later stages of expiring vulcanicity. The entire island 

 is built up of horizontal layers of lava, clay, and coal. The 

 lava beds are from 10 to 20 feet in thickness, and these are 

 separated by thinner beds of the other materials named. There 

 are also with these abundant deposits of fossilised pine trees, 

 and some of the trunks of these trees are two feet in diameter. 

 These horizontal strata enwrap the bases of numerous domes 

 and peaks of grey phonolite, an older volcanic rock. This 

 phonolite is also disposed horizontally, and the peaks are 

 but the remnants of more ancient plateaux which had already 



