R. D. Oldham — Probable Changes of Latitude. 303 



The boulder bed of the Olive group has not yet yielded any fossils 

 of contemporaneous origin, but it appears to be perfectly conform- 

 able to beds of undeniably marine origin, and every argument from 

 analogy is in favour of the supposition that it is itself either of 

 marine or estuarine origin. But, as I have shown above, the land 

 surface of whose waste it is composed lay to the south, so we arrive 

 at the rather startling conclusion that when the beds of the Olive 

 group of the Salt Eange were being deposited, there icere glaciers 

 which descended to the sea-level in a region which now lies within 

 34 degrees of the Equator. 



In that great and almost unknown tract lying between the 

 Aravalli Mountains and the Indus, which is comprehensively 

 entitled "Desert" on the maps, there may be found near the town 

 of Pokran, in N. latitude 26° 55', an old land-surface showing 

 glacial groovings and striae. These might be ascribed to the action 

 of winter coast ice formed on the margin of a lake or sea ; but, in the 

 boulder beds which occur in the neighbourhood, and are without 

 doubt of the same age as the glaciated land surface, there may be 

 found facetted blocks which, like those of the Salt Eange, could not 

 be ascribed to anything but glacier action. Moreover, this land- 

 surface is covered in places by a boulder bed with a hard intensely 

 tough matrix, differing from the stratified boulder beds of the neigh- 

 bourhood in much the same manner as the "till " of Scotland differs 

 from the marine boulder-clays of the Midland Counties ; if the 

 hypothesis that the toughness of the former is due to its being a 

 " Grundmoraine " be accepted, it follows that the same explanation 

 will account for the toughness of the boulder beds of Pokran, and 

 we have yet another proof of the existence of glaciers on this old 

 land -surface. 



The boulder beds in the Desert have been traced for sixty miles 

 north-east of Pokran ; in the vicinity of the old land-surface the 

 boulders are almost exclusively of porphyry and syenite derived from 

 it, but further north blocks of gneiss of the peninsular type become 

 common; and in N. latitude 27° 30', East longitude 72° 30', there is 

 a block of very coarse-grained granite, of which 10 feet x 7-| feet 

 X 3 feet is exposed above ground. The nearest source from which 

 this block could have been derived is in the Aravallis full 150 

 miles away. The age of these boulder beds appears to be the same 

 as that of the Talchirs ; the reasons for this conclusion are of a 

 purely inferential nature, but their extent, combined with the dis- 

 tance from which some of the blocks have been transported, as well 

 as their position on the western margin of the peninsular area, point 

 to the conclusion that they are of marine origin ; so that here again we 

 have evidence of glaciers having descended to the sea in a district noiv 

 less than 27 degrees from the Equator. 



Part II. — General Considerations. 



It has long been known that there were ample proofs of the former 

 existence of mild, even subtropical climates within the Arctic circle ; 

 but the continuity of this climate, and the absence of any signs of 



