182 



♦ KNOWLEDGE ♦ 



[Jlly 1, 1889. 



feeding cattle, horses, &c., only those portions poorest in 

 phosphates are utilised on the farm for litter, kc, and sub- 

 sequently find their way back to the land ia the form of 

 farmyard manure ; whereas the richest portions of the crops, 

 such "as the seeds of most cereals, and edible peas and beans, 

 the tubers of potatoes, and a good share of the roots and 

 hay in the form of meat, are sold off the farm for human 

 consumption, and then the phosphates, along with many 

 other valuable constituents, find their way in the majority 

 of cases to the nearest stream or river, and ultimately to 

 the sea.' The quantity of valuable material lost in this 

 way is enormous. 



If the supply of phosphates available for the plant falls 

 short, then the plant thrives badly, and yields light crops 

 and inferior produce. As an example of this, some 

 data are arranged in the next table, embodying results 

 obtained by Su- John Lawes and Professor Gilbert at 

 Rothamsted. In the first column are given the names of 

 the crops ; in the second the average weights of the yield of 

 these crops when grown on a soil containing only a small 

 quantity of phosphates, but receiving an abundant supply of 

 nitrogenous manure ; in the third column are given the 

 average weights of the yield of the same crops, on the same 

 soil, with the same quantity of nitrogenous manure, and, in 

 addition, a supply of phosphates ; in the fourth column are 

 shown the increases in crop yield obtained by supplying the 

 requisite pjiosphate : — 



The figures speak for themselves as to the amount of the 

 harvests. The quality of the produce is also improved, for 

 example, in the case of potatoes ; the percentage of good 

 tubers is 91 with and 85 without the superphosphate. 

 This table illustrates another point— a point to which atten- 

 tion was drawn in the concluding lines of the article on 

 "Nitrates" in the March number of Kxowledge, p. 102, 

 and which refers to the imperfect utilisation of nitrogenous 

 manures in the absence of other plant-foods in the soil ; it 

 must, however, be borne in mind that the above increase in 

 crops is obtained by the addition of only two important con- 

 stituents of plant-food, viz., phosphoric acid and calcium. 

 Nevertheless, the quantity of nitrogenous manure rendered 

 active by them is very striking. 



Having thus far shown the necessity and the advantage 

 of supplying plants with phosphates, attention will now be 

 turned to the sources of the phosphates for the supply of 

 plants. And here we observe one of those interesting and 

 wonderful compensating influences which are at work 

 everywhere in nature ; for the supply of phosphates for 

 plants is largely, almost entirely, derived from animals 

 past and present, so that in this way animals return to the 

 soil material in a form useless to themselves but upon 

 which plants thrive vigorously and reconvert into a form 

 which is then available for the requirements of animal 

 life. 



The first and, as regards origin, the simplest supply of 



phosphates for plants is found in farmyard manure, stable- 

 litter, sewage, and such like matters which are mainly the 

 rejected products of living animals. The animal consumes 

 in its food amounts of phosphoric acid considerably in 

 excess of its requirements, and consequently when pa-ssing 

 through the body this excess is not digested, and is ulti- 

 mately rejected by the animal along with other indigestible 

 matter and waste products produced in the animal 

 organism. These supplies of phosphates are therefore 

 much mixed up with all sorts of other material, and in fact 

 contain only a small proportion of phosphates. The next 

 source of phosphates is the dead animal, and, as in the case 

 of plants, the phosphates are found in the ash. 'Now flesh 

 contains (speaking very generally, for all kinds of flesh 

 differ to a certain extent in the amount of ash) about 

 •1 to 6 per cent, of ash ; bone, also speaking generally, 

 contains 60 to "0 per cent, of ash ; it will therefore be seen 

 that the latter parts of the dead animal would naturally 

 be looked to to supply most phosphates. 



Bone consists of both organic matter and inorganic matter 

 or ash constituents. If a bone is allowed to soak in dilute 

 hydrochloric (muriatic) acid, all the a.«h constituents are 

 dissolved out, and the bone, while retaining its original 

 shape, becomes translucent and soft, and in fact is then 

 nothing more than a lump of jelly mixed with some fat. 

 If, on the other hand, a bone is boiled in water, it loses all 

 the fat present in it and some gelatin (jelly). This fat is 

 used for making candles ; the gelatin for size. By steam- 

 ing the bones in closed vessels a further quantity of 

 gelatin is extracted and furnishes a kind of glue. By 

 subjecting bone to a still greater heat in a retort over a fire, 

 most of the organic constituents distil off, forming what is 

 known as Dippel's oil, and a residue of carbonised organic 

 matter, " animal charcoal," is left in the retort. But by 

 burning animal charcoal or fresh bones in the air, all the 

 organic matter is consumed and the ash only is left behind. 

 "When bones in these diflerent stages are examined chemi- 

 callvthe amount of phosphates they contain nearly approaches 

 the following quantities : — 



Contain lbs. of 

 Phosphates 



100 lbs. of 

 Fresh bones 

 Boiled bones 

 Steamed bones . 

 Animal charcoal 

 Bone ash . , 



50 

 50 to 60 

 60 to 70 

 70 to 80 

 80 to 85 



However, as might be expected, bones in all these states 

 show great variation in the quantities of phosphates they 

 contain, but the value of bones as a phosphatic manure follows 

 the order above given, bone ash being the best. 



In nature, wherever animal matters accumulate they sufier 

 changes in an order closely resembling that described above 

 in the artificial treatment of bone ; first the most delicate and 

 volatile parts sufier decay, then the tougher portions, until 

 the bones alone remain ; then the bones decay in a similar 

 manner until only the ash constituents remain. 



In past ages such deposits have accumulated, and we find 

 the bones buried in the earth ; they have retained their 

 shape in many cases, but almost always all the organic 

 matter has gone, its place being taken by mineral matter. 

 The deposits are dug up and the material comes into the 

 market as fossil bones ; large quantities come from South 

 Carolina in the United States, also from Cambridgeshire, 

 Buckinghamshire, and Suffolk, in England, from the North 

 of France, and elsewhere. Sometimes the fossils have 

 almost entirely dLsappeared, and the remains have become 

 intimately mixed with the rock : such is often the case in the 

 Belgian deposits near Mons, iu some of the deposits in the 

 North of France, and in other deposits in the neighbourhood 

 of Bordeaux, in Nassau in Germany, and in the west of 



