240 On the Alpine Glacier, Iceberg, [No. 159. 



If Southern India was above the ocean during the deposition of the 

 Silurian rocks, and other fossiliferous strata, of which no remains now 

 exist on its surface, it must have subsequently undergone oscillations 

 by which portions, or the entire mass, including the tract occupied by 

 its grand physical feature, the Western Ghauts, were submerged, and 

 again elevated to their present position with the laterite which, there 

 is every reason to believe, belongs to the tertiary epoch. That at 

 least a portion of Southern India must have been a sea-bed during 

 the cretaceous period, has already been shown. 



Some of the points latterly touched upon in this paper involve, it 

 will be perceived, the highest and most interesting problems in phy- 

 sical geology, which cannot be solved until much more evidence be 

 accumulated regarding the geology and former physical phases of 

 tropical and sub-tropical zones- It has been ascertained beyond doubt, 

 that the seas of ancient periods formerly covered a far greater extent 

 of what is now land in the northern hemisphere, and the contempo- 

 raneous and much greater relative prevalence of land within or near the 

 tropics is supposed, in order to account for the higher temperature 

 which, it is evident, then prevailed in northern regions ; but the pre- 

 sent decrease of which is accounted for by Sir John Herschel on 

 astronomical grounds, viz., that the mean amount of solar radia- 

 tion is dependent on the eccentricity of the earth's orbit, that this 

 eccentricity is, as has been for ages, actually on the decrease ; and 

 with it the annual average of solar heat radiated to the earth's 

 surface. 



Desiderata on the Boulder formation. In the hope of eliciting 

 information touching the occurrence of the boulder formation in 

 India, (and how much might be obtained even from persons en- 

 tirely ignorant of geology now crossing India in every direction,) I 

 have drawn up a few plain directions by which the true boulder 

 formation may be readily distinguished from the ordinary gravels 

 and alluvia of the country ; and have added a list of the principal 

 points on which information is required. 



Sir John Herschel has well observed, " What benefits has not geo- 

 logy reaped from the activity of industrious individuals who, setting 

 aside all theoretical views, have been content to exercise the use- 



