57 



in which night-soil came to be known as a most active fertilizer is so 

 lost in the mist of bygone ages, that we can only conjecture with Lou- 

 don, that man found it necessary to bury it in the earth in order to 

 avoid its disagreeable odour, and immediately observed its effects on 

 vegetation. 



The idea of rendering phosphoric acid more available to plants by 

 partially dissolving various kinds of phosphate of lime in sulphuric acid 

 does not appear to be based upon very sound philosophy. At any rate 

 the manure thus procured has, according to Professor John's researches, 

 little or no beneficial action upon graminaceous plants, though it acted 

 well on turnips.* Moreover, this process of making artificial manure 

 (superphosphate) implies some ignorance of the methods by which the 

 roots of plants absorbs the mineral portion of their nourishment. It 

 appears tolerably well proved that this is effected by the secretion of 

 some vegetable acid, and was well shown by plates of marble exhibited 

 in the Austrian department of the last French Exhibition, where the 

 rootlets of wheat, maize, &c, had left their traces eaten into the marble. 

 Again, M. Cloez, in his recent experiments, caused grains to germinate 

 on blue litmus paper, the course of the rootlets being well marked by 

 pemanent red streaks, which did not disappear on drying, and were 

 therefore not caused by carbolic acid. Moreover, I have observed that 

 all cane soils are naturally more or less acid, and appear to become more 

 so as they approach a state of complete exhaustion. Lastly, it is shown 

 by Professor Deherain ( " Annuaire Scientifique," 1868) that the most 

 insoluble of mineral phosphates, reduced to powder and strewn upon 

 soils deficient in phosphates, increase the yield of the fields at once ; 

 whilst if applied upon soils which contain a due proportion of phosphates, 

 no increase of the crops occurs. The latter fact points very clearly to the 

 importance of knowing something about the natural resources of a 

 soil from which the crops of every kind are regularly raised. 



VI. 



In laying down rules to ensure the highest degree of fertility in our 

 cane soils, we must remember that we are dealing with the life of the 

 plant, and that the phenomena of life are mysteries that no one can 

 solve completely. Hence the danger of adhering too firmly to a favourite 

 theory ; hence, also, the philosophy of following the indications of 

 Natuie as closely as possible. In other terms, we must allow ourselves 

 to be guided by direct experiments independently of any theory. Such, 

 for instance, are those remarkable trials made by Professor Polstorff, in 

 which he found that of all manures known, that derived from the 

 excreta of animals gave by far the highest results.^ All who have 

 devoted their time to this subject are of opinion that rich, well prepared 

 farmyard manure is the most perfect fertiliser known. " We must 

 never forget," says Dr. William Gregory, "that the bed and most 

 economical of all manures is farmyard manure or, what is the same 

 thing, the night-soil and urine of inhabited places." % The reason of this 



* John, " Journ. fur Prak. Chemie," vol. 50, p. 57 (1843 to 1845) ; see also- 

 Lawes and Gilbert's 11 Exp. on Growth of Wheat," 1864. 



f Polstorff, " Annalen der Cheinie," lxii., p. 180 (1847). 



% Gregory, " Handbook of Organic Chemistry," 3rd edit., p. 479. 



