1S39] 



some other portiom of My sort 



105 



bill of lilhomarge confirms me in my views respecting the Tithomargic 

 formation, as entered into in other places. It has resulted from the de- 

 composition of a rock or rocks containing hornblende and felspar — the 

 white showing the felspar — the red the hornblende. Basalt has also most 

 likely been contained in the rock originally, for besides pieces of felspar, 

 of hornblende and of quartz, found lying on the surface of the hill, 

 there were some of basalt. I also picked up one piece of magnetic iron 

 ore. Upon the surface of this hill, or rather mound, are small nodules, 

 of a brown colour and quite hard. On breaking into them they are of 

 the colour of brick, with white specks diffused over them and irridescent 

 blue iron spots and streaks ; they resemble the pebbly looking bodies 

 found in the chlorite rock along v^ith iron stone. Now these indurated 

 specimens seem to be those pieces of the rock before decomposition 

 which contained much iron. By the kindness of my amiable and ex- 

 cellently informed friend Mr. McGrigor of the 39th regiment with 

 whom, in geological brotherhood, I have visited ail the places hi- 

 therto described, I am indebted for some specimens of a similar 

 kind to the last, forming small elevations in the neighbourhood of 

 and beyond Nundidroog. Surface irregular and of a reddish brown 

 colour, internally brick red and resembling burnt brick, with lines, 

 streaks and nests of decomposed felspar, as in the lithomarge just de- 

 scribed, and spots and lines of a blue ferruginous colour. The soil in 

 the neighbourhood of these hills is red and favourable to the growth of 

 tobacco. These hills then seem to consist of a species of iron clay, 

 intermediate between lithomarge and the laterite of the coast. From 

 minute inspection of the rock, and in agreement with former views on 

 the subject, I consider it entitled to the name of laterite, although it is 

 scarcely cavernous. A study of these specimens, shows the passage of 

 indurated lithomarge into clay stone or laterite. If the original trap 

 rock from which it was produced, contained more felspar than hornblende, 

 and not much iron, lithomarge is formed ; but if the rock originally 

 contained more hornblende than felspar and much iron, then the clay 

 stone or laterite is formed. It is this last rock, I should imagine, which 

 is described by Voysey, under the name of iron clay, forming elevated 

 table -land at Beder. 



Nundidroog, distant 35 miles north from Bangalore, rises in three 

 majestic hills from the surrounding plain — at the distance it has 

 the appearance of being only one hill, but there are three—one 

 being thrown back some miles does not deserve to be included. It is 

 said to be 1700 feet high. A peculiar kind of granite was brought me 

 from here, but whether from the hill or not the person who brought it 

 could not say —he thinks it was — he forgot to make a memorandum at 



