1846.] from Seringapatam, to Cannanore. 321 



The third stage shows the felspar reduced to a white clay, and the 

 oxidated hornblende crystals losing their shape, spreading their colour- 

 ing matter in irregular patches through the clay. Where nests of 

 garnets occur, their disintegration imparts a crimson-mottled appear- 

 ance, often seen in the white lithomargic earth3 of the ghauts. The 

 faint violet, or lilac-coloured, spots result from the decay of amethystine 

 quartz or other minerals, impregnated with manganese which imparts 

 this beautiful colour: mica usually imparts a light bright-red. 



Lastly, the whole of the colouring matter — iron, titanium, and man- 

 ganese — become equally diffused through the clay, which is now either 

 of a light ochreous-brown colour, or reddish-brown, according to the 

 greater or less ferruginous character of the rock. Where quartz prevails 

 the decayed mass is more friable and earthy, and the colours are in 

 general lighter than in the clays resulting entirely from the disintegra- 

 tion of felspar rock ; a fact probably to be attributed to the action of 

 the alkali, contained in the latter mineral, on the metallic oxides. 



The red variety of clay prevails most on the hornblendic rocks 

 of the Heggulla pass: near the base of the pass it lies in a stratum 

 twelve feet thick, imbedding angular blocks of hornblende rock, fast 

 decaying. 



It rests immediately on hornblende rock in silti, and is covered by 

 a light brown earth, of mixed alluvial and decayed vegetable matter, 

 intersected by roots of trees, shrubs and grasses, and three or four feet 

 thick. 



The roots of the larger forest trees descend into the clay bed, which 

 is sometimes intersected by crumbly veins of white quartz, which may 

 be seen continued into the substance of the clay from the subjacent 

 bed of rock ; proving the disintegration to have taken place in situ ; 

 and that these clay beds are not the result, in general, of aqueous 

 transportation. Where much iron and quartz prevail, the clay is apt to 

 become cellular, an appearance which must not induce observers to 

 confound it with true laterite. The pass is much steeper than those 

 of Devamunni, Hossamucki, and Bisly, farther north, but is never- 

 theless practicable for lightly laden bullocks. The Bombay army, in 

 1791, advanced towards Mysore by this route, and expended two days 

 in dragging twenty light field guns up two miles, and three weeks 

 to bring up fourteen battering guns with their tumbrils, none heavier 

 than eighteen-pounders. Near the bottom of the pass, the true laterite 



