unless he wishes to run the risk of throwing away his money, he should buy guano from such sources only as are known to be undoubtedly trustworthy, or after a previous chemical examination. If he is not afraid of a little time and trouble, he can institute a trial for himself very easily. Tests are now possessed of such simplicity as to require scarcely more dexterity and attention than roasting or boiling coffee, and yet sufficiently accurate to serve in doubtful cases as reliable guides. 1. Test by drying and subsequently washing with water. If the guano, as is generally the case with those kinds that are brought from Peru and Chili, is a uniform powder, weigh out two ounces, spread it upon paper, and let it lie for two days in a moderately warm place, in summer in a dry and airy situation, in winter in a warm room or chamber, in order that the air may dry it. What it may then have lost in weight must be esteemed superfluous water. Many sorts of guano are so moist as to lose by this gentle drying from three to four drachms (20 to 24 per cent.) in their weight. If the guano, like the Patagonian and African, is not of uniform character, then, in order to obtain a mixture as equable as possible, the lumps, which have frequently an altogether different composition from that of the powdery portions, must be broken in pieces and pulverized, before weighing off and drying a given quantity. In like manner care must be taken to distribute stones, feathers, &c., when they are present, equably throughout the mass. As the stones are often so firmly stuck over with the guano that they can only be freed from the latter by tedious scraping, it is advisable to pour hot water over a distinct portion in some convenient vessel, and to let it soften by standing for a night, upon which stones and sand will remain behind after agitation and washing with water. 2. Test by combustion.-Pour half an ounce of the guano to be examined into an iron spoon, and place it upon red-hot coals until a white or grayish ash is left, which must be weighed after cooling. The less ash is left behind, the better is the guano. The best sorts of Peruvian guano yield, from half an ounce, somewhat more than one drachm of ashes (30 to 33 per cent.); whereas the inferior guanos that are now so often offered for sale (for example, Patagonian, African, Saldanha Bay, and Chili guanos) leave a residue of from 23 to 3 drachms (60 to 80 per cent.), and those intentionally adulterated a still greater quantity of ashes. Of genuine guano, the bad as well as the good, the ash is always white or gray; a yellow or reddish colour indicates an adulteration with loam, sand, earth, &c. The test is very simple, and at the same time very trust. worthy; it rests upon the fact, that the nitrogenous combinations existing in guano, and forming, as has been demonstrated in a preceding section, its most valuable ingredients, undergo combustion and volatilization when subjected to heat. Here, too, the difference of odour during the combus tion is characteristic. The vapours from the better specimens have a pungent smell, like spirits of hartshorn, with a peculiar piquancy, almost like old Limburg cheese (decayed); whilst those rising from inferior varieties smell like singed horn-shavings or hair. A The combustion may be undertaken on any hearth or in any parlour stove, without fear in the latter case that a disagreeable odour will be diffused throughout the room. brick should be firmly thrust down into the fire, and the spoon laid upon it in such a way that the handle rests upon the brick, and the bowl with the guano projects free over the fire. A cork should be fixed on to the extremity of the handle, in order that the hand may not be burnt when brought in contact with the heated spoon. 3. Lime test.-Put a teaspoonful of each kind of guano to be examined into a wineglass, and upon this a teaspoonful of slaked lime; then add a few teaspoonfuls of water and agitate the mixture briskly. Lime liberates the ammonia from the ammoniacal salts contained in the guano, in just the same manner as from rotten muck and putrid drainings (page 82), and this escapes; the more excellent, therefore, a guano is, the stronger will be the pungent ammoniacal odour which escapes from this guano paste. This test does not indeed possess the accuracy of the preceding, but is still in many cases very convenient on account of its simplicity, and more particularly where it is desirable to pass a general and approximative opinion upon the quality of different kinds of guano. Under present circumstances, especially, its utility appears the greater, because guano of intermediate quality is now of very infrequent occurrence, and commerce pre sents us for the most part with remarkably good or remarkably bad qualities, in examining which the lime test can be advantageously used, inasmuch as the difference in the strength of the odour is really so remarkable, that it cannot escape the detection of the most unpractised nose. In order to be able to apply this test at any moment, it is judicious to keep a portion of slaked lime constantly on hand. But that this may not lose its effect, it must be carefully excluded from the air, and should, therefore, be preserved in a dry and well-corked bottle. 4. Test with hot water.-Make a filter of blotting-paper, folded together into the shape of a cone, and put this into a tin-funnel or wire triangle. Let half an ounce of the air-dried guano be placed in this, and over it poured hot, best boiling water, as long as it passes through of a yellowish colour. If the paper with the moist guano is laid, when no more liquid drops from it, in a warm place, and the residue weighed when it has become completely dry, the deficiency from half an ounce will show the weight of those elements which have been dissolved by the water. As a general rule it may be held, the larger the quantity of a guano that is dissolved in water, the more ammoniacal salts does it contain, and the better it is. Hence that guano must be preferred, as in the test by combustion, which, upon being so treated with water, leaves behind the smallest residue. In the best or Peruvian guanos, the residue from half an ounce that is insoluble in water amounts to about 2 drachms (from 50 to 55 per cent.); on the other hand, in the comparatively worthless guanos from 3 to 3 drachms (80 to 90 per cent.). Exceptions to this rule may, however, occur, namely when a guano contains many soluble mineral salts. Specimens have been met with in commerce which consisted to the extent of one-half or two-thirds of sea-salt and Glauber salt; such guanos, upon being treated with hot water, would only leave a residue of from one to two drachms of insoluble substances, yet must, nevertheless, be regarded as anything but good merchandise. In such a case most complete security is afforded against an erroneous decision, by the use of the combustion test described above (p. 134); for then it would be found that a guano of the kind in question yielded three drachms and more of ashes, and must accordingly be admitted as an inferior variety. 5. Vinegar test.-Pour strong vinegar, or, better still, some muriatic acid, over the guano to be examined; if a strong effervescence ensues, an intentional adulteration of the guano with lime may be inferred. This substance may also be recognized by the combustion test, since lime remains behind in combustion and augments the quantity of ashes. On the best sources for obtaining guano little positive information can be given, since the bad may be carried everywhere as easily as the good, and since admixtures and adulterations may be made in every place. Good Peruvian guano can only come to Europe through a single English firm (Gibbs, Bright, and Company, London), who have made a contract with the Peruvian government which gives them the exclusive sale of this guano. Whoever may desire to obtain more precise information upon this important manure and the results it has produced in Saxony, will find it given in the little work entitled Guanobüchlein (little guano-book), which contains instructions. for the use of German farmers, upon the constituents, action, tests, and employment of guano, written by A. Stöckhardt, Leipzig, and published by George Wigand, 1851. IX. BONES. COMPLAINTS are often heard, that, by the consumption of English yarn in Germany, thousands of English workmen are supported by German money. Germany has done far more; for nearly half a century it has given corn to English workmen, by the exportation of German manure, German bones, and German oil-cake. According to trustworthy information, the produce of English fields since the importation of bones and oil-cake has been doubled. The strength which has been lost to our country by this exportation of manures would assuredly have been preserved to it, if during this period the importance to agriculture of the constituents contained in bones and oil-cake had been clearly understood in Germany. This is the triumph of intelligence, that it makes powers serviceable which remain neglected and useless where intelligence is wanting. That German bones exert a vigorous manuring influence upon German soil can no longer be doubted; for the results of practical experiment are now before us to a sufficient extent to convince every one who is open to conviction. Manuring with bone-dust has become general over all parts of Saxony during the last fifteen or twenty years, since the produce obtained by its employment in Upper Lusatia first showed its extraordinary utility. How important an extension this mode of fertilizing land has obtained in that part of Saxony more particularly, is revealed to us by the fact, that the first bone-mill constructed there by an intelligent farmer ground a total of 600 cwt. during 1837, but in the year 1848 some 15,000 cwt.; as also by the additional consideration, that in the last-mentioned year, in Lusatia alone, some 50,000 or 60,000 cwt. besides were prepared and sold, yet without satisfying all demands. The total quantity of bones which are to be obtained from the animals annually slaughtered in Saxony amounts, on an approximative calculation, to 100,000 cwt., and half this quantity, if not still more, is imported from the immediately adjacent countries. If, on a moderate assumption, the total produce which is gained from 1 cwt. of bone-dust is estimated at 2 Saxon bushels of rye (6 English bushels), the quantity of this substance that is yearly consumed in Saxony leads to an increased yield of 300,000 bushels of rye. 1 1. COMPOSITION AND EFFECTS OF BONE-DUST. Bones consist of an earthy tissue of minute cells, in which is included an organic substance called gelatine. Gelatine contains a great amount of nitrogen, and readily putrefies when moistened with water and exposed to the air; in this way the nitrogen becomes assimilable by plants, and causes an extremely rapid and vigorous vegetation, as may be readily observed by pouring glue-water or meat-broth upon any flower. The forcing power which finely powdered bone-dust exercises upon vegetable growth is owing to the gelatine it |