All the guano islands are uninhabited, except by the laborers, mostly Indians or poor Chinamen, who are employed in the work of digging, carrying and loading the guano into the ships. When a vessel is ready to take in cargo, she is moored alongside of the rocks almost mast head high, from the top of which the guano is sent down through a canvass shute directly into the hold of the ship. Thus several hundred tons can be put on board in a day. The trimming of the cargo is a very unpleasant part of the labor. The dust and odor is almost overpowering; so the men are obliged to come often on deck for fresh air. The rule is to remain below as long as a candle will burn; when that goes out, the air is considered unfit for respiration. If the labor had to be performed by a Yankee, he would think it unfit at first; and thereupon set his ready wit at work to construct a machine to spread the guano as it fell, from one end of the hold to the other. The guano in position upon the island, is so compact it has to be dug up with picks. It is then carried to a contrivance made of cane, at the edge of the rock, which conveys it into the canvass conductors. The mass is cut down in steps, receding and rising from the point of commencement, and has not yet attained a depth of 100 feet, and with all the labor of hundreds of men digging, and numerous ships carrying away to the several countries using it, there is but a bare beginning of removal made upon the mass upon one island only, as may be seen by reference to the diagram. Supposing like many others, the supply of Peruvian guano was like the Ichaboe, destined to run out--that is all be dug up and carried away; we inquired of an intelligent captain of a ship just returned with a load, how long it would be before the supply would be exhausted. "Exhausted!" said he, with a look over the gangway, as much as to say how long would it take to exhaust the ocean with a pint cup; "why not in one hundred years, if every ship afloat should go into the trade, and load and unload as fast as it would be possible to perform the labor; no, not from the Chincha islands alone. Exhausted! they never will be exhausted." With due allowance for the captain's enthusiasm, we may be very certain from the government surveys, the quantity is so great, that no probability exists of the supply being exhausted until all the present inhabitants of this earth have ceased to move upon its surface. We may be certain of another fact; that unless we commit a great national wrong upon Peru, by seizing upon some of her guano territory; a thing which the sober second thought of this nation will never sanction; we shall not be able to obtain the article only through her government agents, at such prices as her rulers think proper to affix to it. While the demand and the result of the use of guano continues as at present, there is not much probability of any material change.