To the south of Lima, in the Bay of Pisco, are found three small islands, or rather barren rocks.  Not a tree grows on them--not a blade of grass.  The feathered race for ages past, probably since the last flood rolled over the face of the globe, have made them their abode. Strange as it may seem, they are of more intrinsic value than the richest mines of Potosi; yet their produce is all on the surface, and to be obtained but with little labour.  They are the three Chincha Islands, and their produce is guano.  It is the result of the droppings of birds, which in that dry and rainless region has preserved all its fertilising qualities, and has been stored up, by the decree of a beneficent Providence, to restore strength and vigour to the far-off lands of the Old World.  We sighted them one morning, and running in, brought up in their neighbourhood.  There were sixty ships, mostly English, anchored near them, for the purpose of loading with guano; and sometimes there are upwards of a hundred.  A boat was lowered, and the captain, Jerry, the doctor, and I, went in her.  We had to climb up to the top of one of the islands by a ladder; the cliffs are so steep, and being composed of felspar and quartz, so broken away by the action of the sea, that it is the only method of reaching the summit.  The island was covered with thick layers of guano, and one cutting, about a hundred yards from the cliff, was sixty feet deep, or rather high, for the cutting is made into it from the side, just as a slice is cut out of a cheese.  A steam-engine is employed in digging it out, and filling a set of cars, which run on a tramway to the edge of the cliff under which the vessels lie to load.  Two hundred convicts were engaged in shovelling down the guano, and a number of stout negroes are employed in the hold to distribute it as it comes down through a canvas shoot.  They have to wear iron masks, as the fresh guano is stronger than volatile salts, and more penetrating than coal-dust.