The adulteration of guano is carried on to a very large extent; and though perhaps not quite so extensively now as it was some years since, it is only kept in check by the utmost vigilance on the part of the purchaser. The chief adulterations are a sort of yellow loam very similar in appearance to guano, sand, gypsum, common salt, and occasionally also ground coprolites and inferior guano. These substances are rarely used singly, but are commonly mixed in such proportions as most closely to imitate the colour and general appearance of the genuine article. The extent to which the adulteration is carried may be judged of from the following analyses taken at random from those of a large number of guanos, all of which were sold as first-class Peruvian. Water 12.85 15.19 12.06 27.86 6.32 Organic matter and } ammoniacal salts } 26.84 44.31 34.14 30.41 27.42 Phosphates 15.54 20.95 22.08 22.17 33.61 Sulphate of lime ... ... 11.08 ... 22.11 Alkaline salts 6.07 9.40 12.81 7.92 22.50 Sand 38.70 10.15 7.83 1.64 10.15 ------ ------ ------ ------ ------ 100.00 100.00 100.00 100.00 100.00 Ammonia 9.34 13.90 9.77 8.64 9.76 In all those cases a very large depreciation in the value has taken place, and several of them are worth considerably less than half the price of the genuine guano, while they are generally offered for sale at about L1 under the usual price. The adulteration is chiefly practised in London, and cases occasionally occur which can be traced to Liverpool and other places; but it always takes place in the large towns, because it is only there that facilities exist for obtaining the necessary materials and carrying it out without exciting suspicion. The sophisticated article then passes into the hands of the small country dealers, to whom it is sold with the assurance that it is genuine, and analysis quite unnecessary. In other instances, adulterated and inferior guanos are sold by the analysis of a genuine sample, and sometimes an analysis is made to do duty for many successive cargos of a guano which, though all obtained from one deposit, may differ excessively in composition. In order to insure obtaining a genuine guano, it is above all things important to deal only with a person of established character, who will generally, for his own sake, satisfy himself that the article he vends is genuine and of good quality; and it is always important that the buyer should examine the analysis, and in all cases where there is the slightest doubt, should ascertain that the bulk sent corresponds with it. In the case of a Peruvian guano, a complete analysis is not necessary for this purpose; but an experienced chemist, by the application of a few tests, can readily ascertain whether the sample is genuine. Where the difference in value between different