Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/362



1. A crystalline limestone which burns to a white lime mixed with brown spots, falling very readily to powder. 100 grains dissolved in dilute acid left 7 grains of residuum, which consisted of about 4 grains of oxide of iron, the remainder being silica.

2. The preceding variety mixed with a considerable quantity of quartz, and of yellow calcareous spar. This latter substance occurs also in veins and probably pervades all the calcareous strata. A piece of that stone when thrown into dilute acid leaves a fragment which does not fall into powder.

3. This variety is intermixed with a smooth slaty substance with an unctuous feel, which is probably talcose slate: it leaves: considerable quantity of large grains of quartz when thrown into dilute acid.

None of these calcareous strata are used for any other purpose than to mend the roads, and they do not seem to be known as limestones, most probably because there is a much better limestone so near at hand. The first variety would yield a very good lime, if reliance for that purpose can be placed on my minute experiments; a trial on the large scale might very easily be made in one of the neighbouring lime kilns. The principal calcareous stratum is five feet thick.

Immediately behind the village of Bagborough I found a calcareous stratum occurring in the same way as those at Halsey cross.

§ 19. My observations were principally confined within the limits I have already mentioned, but having had an opportunity of making a cursory examination of the country between Porlock and Ilfracombe, and as the rocks occurring in that part of the country are connected with those I have been describing, I shall briefly state the few notes I made. My route was from Porlock, by Culbone,