310 



On the Laferit'ic Formation, 



[Oct. 



two, \vith true granite and pegn^alite, tbrough wliidi last ])asalt has 

 frequently iiU-uiuated itself (none of tlie rocks that I liave ever seen on 

 the hills,- but ceriainly helow, are deserving the name of hornblende 

 slate), there is anotlier, very common, named by Dr. Benza hceniatitic iron 

 ore, I feel tliat I am almost presumptuous in calling in question the 

 €orrectness of Dr. Bcnza's nomenclature for the last, being conscious of 

 my deficiencies, but in all investigations afier truth, the name attached 

 to things is of more consequence than any consideration for the name of 

 individuals, hov/ever eminent. What Dr. Benza calls hoemalitic iron ore 

 I will now describe, having visited its various localities, some of which 

 are not mentioned by hifn. It is generally found in situ, towards the 

 top of the small hills, although detached pieces are frequently at the 

 bottom. It protrudes about two or three feet from the ground ; I have 

 seen it in one place more than 8 or 9 ; and is covered with lichens of 

 various colours — the size of tliese rocks and their grouping together, 

 similar to quartz rock in general — the surfece irregular and full of cavi- 

 ties, with ragged elevations — -those detached and lying on ihe ground 

 shewing a more irregular surface, the result most likely of water lodging 

 on them more easily than on tlie fixed rock — the interior is almost always 

 of a brown colour — the aspect of the rock, both externally and internally, 

 sometimes brown yellow or reddish, generally the former, and sometimes 

 all the intermediate shades — small holes, like pin-holes, are scattered 

 Over the whole internal surface, which in some specimens are not very 

 distinct, and small specks of undecomposed quartz are distributed over 

 the whole in the same way. In one specimen before me, the surface is 

 irregularly pisiform — the pea-shaped aspect weathered down— the interior 

 not so solid as the others, fuller of pieces of undecomposed quartz, and 

 it has one or two cavities containing a dark brown or purple earth, ap- 

 parently a driiSy cavity of titaniierous iron ore decomposed ; and it is to 

 the falling out of the decomposed substance from these cavities, that, in 

 some of the specimens, which approach close upon laterite, will account 

 for the cavernous appearance, which was previously referred either to 

 the irregular junction of the quartz pebbles or to the falling out of the 

 softer parts. These are, ther efore, the three modes by which to explain 

 the tubular and cavernous aspect of laterite, viz. the irregular junction 

 of the quartz pebbles or crystals, the falhng out of the felspar and 

 softer parts, and the existence of drasy cavities of iron ore in the 

 original rock. Many specimens of this so named htematitic iron ore 

 have all the peculiar features of true laterite, in as great a degree as 

 those on the coast, with which a comparison has been made. This leads me 

 to the nature of this lisBraatitic iron ore. and to that also of Dr. Ben^a's 



