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of the former. This process has no doubt been going on for many ages, as the great number of strata of which the Island is composed demonstrate—as they stand now quite perpendicular, it is further evident that they were afterwards upheaved by plutonic power. Their strike is S. to N., possessing a thickness that varies very much. The strangest appearance in the white limestone are the round holes, from 1/2 of an inch to 6 and 8 inches in diameter, produced probably from the emanation of gases. The sides of these holes, as well as those of the phosphatic beds, are covered with a crust of pure phosphate of lime, reaching a thickness of over half an inch.
The rocky kind of phosphate contains a few grains of yellow and blackish sand, but no remains of fossils of any kind are perceptible, having doubtless been destroyed by the action of the heat that existed at the time of the upheaval.
On the outcroppings of the limestone strata, the phosphatic minerals appear in nests of very irregular forms and sizes, as shown by sketch C. The greater part of them widen considerably in descending, and are finally cut out. See sketch D. I am, however, of opinion that, by removing the limestone intervening, similar nests will be found underneath, as it must be taken for a certainty, that the phosphate of lime running parallel with the strata of the carbonate of lime, will extend as far as the latter, a presumption partly proved, at a point right close to the level of the sea, on the N. W. side of the island, where the surf has washed away a part of the limestone and exposed a large stratum of rich phosphate, at a distance of over 250 feet from the top of the island.
On the lower flat the greyish phosphate is predominant; on the upper one the reddish brown. At innumerable places the hard undecomposed phosphate of lime crops out, from which, as well as from the fine, samples have been taken indiscriminately by Doctor Liebig, for the purpose of obtaining perfect and correct average ones.
Working of the Phosphatic Deposits.
The working of the phosphate of lime since its commencement, about nine years ago, proves clearly how easily and cheap this mineral can be sent to market. Pick and shovel are the only tools needed. After the upper part, generally mixed
