a Mddlatiott^^'^ddi^j'^hA^b^he' ground at present' cont«iiBi^tlijgl|Ie 

 phbsphbric afeid for riiifetcehicrbps of barley of the salue^aA«»UIiri(*B'w 

 thb average of those of the permanent crops, and ^fthfeiBaraei<5uiriityilf 

 a^ that Obtained' in 184'4''. It was also found, that ^hepe'wasiE^'Siipplyp 

 of potass sufficient for fifteen crops of barley ; of «odaf for fbrtyi^v^n 

 arid of magnesia, for thirty-four. Whenj ho*weveii, we eiaiirfweiotpi' 

 m'uch of these ingredients is taken up by water containing carbonreli 

 acid, the proportion of each is found to be much smaller ; and 'a-' > 

 striking difference exists, in this respect, between the soil which haul" 

 been recently manured and that which had been drawn upon by &><-' 

 sufecessidn Of crops. In the first case, the quantity of alkaline siil- 

 phate obtained in the pound was 3*4 gi-te. ; in the latter it varied froiw'! 

 0*7 to 0*07 ; and of phosphate, the quantity in the former was abotif '> 

 0*3, whilst in the latter it varied from 0-18 toG'05. •'•nanlii-' 



From these facts the author concludes, first, that the falling 'OffJftf J 

 a crop after repetition depends, in some degree, on the less ready"! 

 supply of certain of the inorganic ingredients which it requires foP' 

 its constitution ; but that two crops equally well supplied by the soil 

 with these ingredients may take up different quantities of them, ac- 

 cording as their Own development is more or less favoured by thfl)i 

 presence of organic matter in the soil in a state of decomposition. <;^' 



Secondly, that it is very possible that a field may be unproduc»Jin 

 tiVe, although possessing abundance of all the ingredients requirOd'i 

 by the crop, owing to their not being in a sufficiently soluble forrid'^'f 

 arid therefore not directly available for the purposes of vegetatiorif^' 

 so that, in such a case, the agriculturist has his choice of three'^ 

 methods ; the first, that of imparting to the soil, by the aid of manurejib 

 a sufficient quantity of these ingredients in a state to be immedi^ < 

 ately taken up; the second, that of waiting until the action of de- 

 composing agents disengages a fresh portion of those ingredients 

 from the soil (as by letting the land remain fallow) ; and the third, 

 that of accelerating this decomposition by mechanical and chemical 

 means. '*-'" '^" 'i'""" ^iji'-j i'^ui ^i^-i' ^j") :' • i 'von. id .iiti,<!a'+'( 



Thirdly, that it is probable that in most districts ^sufficient' 

 supply of phosphoric acid and of alkali for the purposes of agricul- 

 ture lies locked up within the bowels of the earth, which might be 

 set at liberty and rendered available by the application of the arti- 

 ficial means above alluded to. 



■'Fourthly, that the aim of naturo seems' to be to bring into this 

 soluble, and therefore available condition, these inorganic substances 

 by animal and vegetable decomposition, and therefore that we are 

 counteracting her beneficial efforts when we waste the products of 

 this decomposition by a want of due care in the preservation of the 

 various excrementitions matters at our disposal. 



Fifthly, that although we cannot deny that plants possess ^ the 

 power of substituting certain mineral ingredients for others, yet that 

 the limits of this faculty are still imperfectly known, and the degree 

 in which their healthy condition is affected by the change is still a 

 matter for further investigation. 



Lastly, that the composition of various plants, as given in this 



