THE FARMER'S MAGAZINE. 



231 



from 10 to 14 grains ; that is to say two-thirJa of the guano 

 remain in place of one third. This is by far the most accurate 

 and conclusive method of testing a Peruvian guano ; but it 

 must be distinctly understood to apply to that variety only. 

 When any of the other kinds are examined, it is important 

 to bear in mind that the colour is a character of very little 

 value ; as a general rule, indeed, it is desirable that they 

 should be pale and of a brownish rather than a grey colour, 

 but no conclusions can be drawn from this as to whether it 

 is damp or not. The best method of testing is to burn a 

 small quantity in a capsule untd the organic matter is com- 

 pletely burnt off; and though no conclusions cau be drawn 

 from the proportions of fixed and volatile matters, it is 

 advisable to take always about the same quantity, which 

 may be as much as will lie on a shilhng, so that the observer 

 may be able to institute some sort of comparison between 

 different samples. When burnt the residue should be white ; 

 if it is brown or reddish like brickdust, the sample is pro- 

 bably either adulterated or of a very iuferior kind. It is 

 then shaken out into a wine glass or other convenient ves- 

 sel, and about half a teaspoonful of water poured upon it, 

 and as soon as it has become thoroughly moistened about a 

 teaspoonful of muriatic acid (spirit of salt) is added. If it 

 effervesces the guano contains chalk (carbonate of lime), or 

 has either been adulterated with that substance, or is one of 

 the inferior varieties which contain it naturally. If it does 

 not effervesce the glass is left in a warm place for an hour or 

 two, and then a little more acid and water are added, and it is 

 as;ain allowed to stand. The whole should now be dissolved, 

 with the exception of a few grains of sand. If the guano 

 stands all these tests, it is in all probability genuine ; but of its 

 quality we get no information, for it may be worth £7 up to 

 £10, or even £12 per ton, if a phosphated guano, and from 

 £12 to £15 if Peruvian, according to the proportions of its 

 valuable constituents ; that, of course, can only be decided by 

 an accurate analysis, without which no prudent man wdl pur- 

 chase a guano, but he will take care to make the expericnents 

 we have just described with the analysis in his hand. Thus, 

 if he find that the ash of his guano effervesces on the addition 

 of acid, and no mention is made of carbonate of lime in the 

 analysis, his suspicions will naturally be awakened. So, like- 

 wise, he will be able to form a rough guess as to the corre- 

 spondence between the sand he finds and that stated in the 

 analysis ; but it will be necessary for him to be careful should 

 the guano contain sulphate of lime, part of which will, in the 

 method of treatment just described, remain undissolved and 

 mixed with the sand, for ascertaining the presence of the 

 latter substance, however, there is no satisfactory test which 

 can be put into the hands of the farmer. The chemist uses 

 chloride of varium for detecting it, but the mere precipitation 

 by means of that substance is not conclusive in the case of a 

 guano, as it may contain alkaline sulphate, which gives the 

 same reaction. Commou salt is occasionally, though 

 rarely used for adulterating guano, and it can gene- 

 rally be observed in grains throughout its mass, and the 

 taste of the particles picked out of it is, on the whole, 

 the most convenient mode of determining its nature. 

 It appears, then, that provided a guano be of a kind dis- 

 tinguished by general uniformity of composition, it is pos- 

 sible to test its purity with some degree of accuracy, but 

 this occurs only with Peruvian ; and, though ' a few 

 experiments can be made, by means of which the grosser 

 impurities of the other sorts of guano may be detected, 

 it is necessary to bear in mind that in the latter case these 

 substances may be naturally present, and hence the farmer 

 will not rashly bring a charge of adulteration against the 

 seller, although he may with justice complaiu of the inferiority 

 of the article. As far as my experience goes, Peruvian guano 

 is the only variety which is deliberately adulterated ; and it 

 is selected because it is more commonly bought without 

 analysis than any other variety, and because the inferior 

 guanos are often so low in quality that they will not bear fur- 

 ther deterioration. With the inferior guanos I believe there 

 is no safety except in complete analysis, because the question 

 generally is, not whether they are adulterated, but whether 

 the farmer gets fair value for his money. All the difficulties 

 which occur in testing guano are met with to a still greater 

 extent in superphosphates, where we have to look not merely 

 for ammonia and phosphates in their ordinary condition, but 

 also in the form of soluble phosphates, and then mixed with a 



variety of other substances iu the most variable proportions. 

 Their complexity is, indeed, so great, that no kind of testing 

 can be considered satisfactory ; nor is it even possible to 

 judge by external appearance, for the differences between 

 genuine and good samples are very great indeed. We may 

 judge to some extent of the quantity of moisture by pressing 

 the substance in the hands, or, better still, by beating it in a 

 mortar, when it sometimes goes into a pasty mass ; but even 

 this is not a proof of inferiority, for some very good super- 

 phosphates are extremely damp. In short, so great are the 

 variations that uothiog but an exact determination of the 

 quantities of soluble and insoluble phosphates will give any 

 reliable information. Nor is it possible to give rules by which 

 inferiority can be detected, and the farmer is forced to come to 

 the chemist, and he places in his hands what is one of the 

 most difficult and tedious anslysea in the whole range of che- 

 mistry. To the various other substances used as manures, 

 such as coprolites, bone ash, flesh manure, and a host of others, 

 no tests can be applied by means of which their quality can 

 be ascertained, and it is absolutely necessary to determine the 

 exact proportions of each of their valuable constituents ; but 

 as these substances are comparatively seldom used by the 

 farmer, it is of less importance for him to do so. From what 

 has been said the obvious inference is that the great bar to 

 the testing of most manures is their extreme complexity. 

 Whenever they are simple in composition, as is the case with 

 the salts of ammonia or nitrate of soda, methods of examina- 

 tion can be made use of, which are very easily executed ; 

 but just in proportion to the number of different ma- 

 nurial substances present does the difficulty of test- 

 ing increase. If we add to this also the fact that a 

 large proportion of all the more complex manures consist of 

 substances which yield little or no value to the farmer, but 

 which he is compelled to take because they exist in the natural 

 mixtures employed as fertilizers, he will readily appreciate the 

 necessity for a more elaborate and complete examination than 

 it is possible for him to make. And for this reason, also, the 

 complex manures are those most frequently adulterated ; for 

 the dishonest dealer, when detected, has always the opportunity 

 of falling back upon the admitted variations in their composi- 

 tion, and declaring that the substances detected by analysis 

 are those naturally existing in the manures. Along with these, 

 a complex manure haa another disadvantage, in so far as the 

 purchaser is compelled to take a mixture which may not be 

 that best suited to the soil or crop to which it is to be applied. 

 It must be admitted, no doubt, that a manure ought to contain 

 all the different constituents of a crop which is to he raised 

 by means of it ; but in'actual practice a soil may be deficient 

 in one substance, which alone requires to be added. It is true 

 that those not immediately required may become available to 

 future crops ; but in the meantime they are liable to a greater 

 or less loss in the soil, and would be much more economically 

 applied if they could be reserved tdl the time at which they 

 are wanted. The perfection of manuring would be arrived at, 

 if each individual constituent of the food of plants could be 

 purchased separately, so as to place the farmer in the same 

 position with them as he is with seeds ; but just as the indi- 

 vidual who is about to lay down laud in grass does not pur- 

 chase for this purpose a miscellaneous jumble of grass seeds, 

 but selects only the species he knows from experience to be 

 most advantageous, and mixes them in proper portions, so he 

 would choose such quantities of each manurial substance aa 

 experience teaches him to be best adapted for his soil. Al- 

 though this would, no doubt, be the most advantageous way 

 of employing manures, I must by no means be supposed 

 to assert that we are at present possessed of sufficient 

 knowledge to enable us to make the most suitable mix- 

 tures; but the cause of our ignorance on this point lies 

 in the complexity of our present manures, which prevents 

 our having the opportunity of making our experiments 

 upon each individual constituent, or upon definite mix- 

 tures ; and I have no hesitation in saying, that if at the 

 present moment the important components of manures 

 were to become separate articles of commerce at such prices 

 as would permit their use by the farmer, the next ten years 

 would show a very important addition to our knowledge of 

 both the principles and practice of manuring. It ia scarcely 

 necessary to observe that there is no prospect of such a change 

 occurring, but it should, in the meantime, indicate the direc. 

 tion in which the improvement of manures ought to be carrieds 



