SAN LORENZO. 595 
In this short space of one hundred and eighty feet, there are eight 
layers of sandstone alternating with shales of different colours. 
Figure 2 represents another cliff, the height of which is but forty- 
five feet. It is situated a short distance to the north of the harbour, 
on the east-northeast side of the island. ‘The following alternations 
were there observed, commencing above :— 
. 15 feet.—Sandstone ; grayish, 
2 feet.—Shale; light bluish. 
. 10 feet.—Sandstone ; grayish. 
4 feet.—Shale ; bluish above, in other parts red. 
foot.—Sandstone ; grayish. 
feet—Shale ; mostly red, dirty yellowish above. 
feet.—Sandstone ; grayish. 
foot.—Shale ; light bluish. 
Sandstone. 
Caraga ene 
Se Qo rfF 
Such alternations occur everywhere through the island. 
In some places, however, there is a cliff of eighty feet, consisting 
wholly of shale, as may be observed a short distance north of the cliff 
just described, where the following varieties of shale were noted down. 
Eleven feet, dirty yellowish and brownish; nine feet, alternations of whitish with 
brownish and yellowish; twenty feet, dark bluish; fifteen feet, dull greenish ; twenty-five, 
dark bluish shale. 
The cliff at the northern point of the island consists of a dark, com- 
pact blue-black shale, passing into a fine schistose sandstone. 
The colours of the sandstone are sometimes arranged in parallel 
stripes, and frequently in concentric curves. ‘The red bands thus 
formed are very distinct on the worn stones of the beach. They indi- 
cate a concentric structure in the arrangement of the colouring ingre- 
dient—the oxyd of iron. 
Structure.—One of the most striking characters of this rock is the 
regularity of its fissures, producing, in some cliffs, vertical planes of 
fracture, of uniform character, through a height of a hundred feet. In 
a distant view, the rocks intersected by these vertical fractures have 
much resemblance to basaltic rocks. They were most distinctly of 
this character at the northern point of the island, though observable 
also elsewhere. 
There are generally two systems of fissures, dividing the rock into 
rhombic fragments; and sometimes another cross fissure occurs, 
