554 



Agricultural Chemistry— Turnips. 



The knowledge which we at present possess of the amount, the 

 composition, and the office of the mineral matter found in com- 

 bination with the various definite organic compounds of which the 

 solid and fixed substance of a plant is made up, is very limited ; yet 

 lis such as by no means leads us to assign to all the constituents 

 of the ash of a crude vegetable product an essential position in 

 the constitution either of the parts aheady elaborated, or of those 

 which would result from the continued growth of the plant. It is 

 obvious that an examination into the nature and constancy of the 

 circumstances of growth, vath which variations in the quantity and 

 composition of plant-ashes are connected, cannot alone provide an 

 explanation of the uses and importance of the mineral substances 

 in the plant ; it is, however, an essential step in the inquiry, and 

 the results attained by it must materially direct and aid any col- 

 lateral course of investigation. 



In entering at once upon this part of our evidence, we may 

 again state that we did not determine the amount of dry matter in 

 the produce of the first two seasons' experiments : we are unable, 

 therefore, to give the percentage of ash in the dry matter in the 

 specimens of those two seasons, and it will afterwards be seen that 

 this particular is more significant than that of the percentage in the 

 fresh produce. On this account, and as we wish to compress our 

 matter as much as possible, we shall not give any statement of the 

 results of those two years, but only remark that a close examina- 

 tion of them affords like conclusions to those to which the third 

 season's experiments lead us. 



The percentage of ash in the fresh bulbs, the mean of the pro- 

 duce of each of the four conditions of manuring, frequently 

 referred to before, are given below. 



General Description of Manuring. 



Percentage 

 of Ash in 



Fresh Sub- 

 stance of 

 " Norfolk 

 White " 

 Turnip 

 Bulb. 



Season 1845. Mean of 13 experiments by purely mineral manures 

 Season 1845. Mean of 13 experiments by mineral manures and rape-cake | 



added. . * j 



Season 1845. Mean of 13 experiments by mineral manures and ammonia-^ 



cal salt j 



Season 1845. Mean of 13 experiments by mineral manures, and both am-l 



moniacal salt and rape cake j 



0-58 

 0-57 



0'61 



0-60 



These results are the actually found percentages of ash, without 

 any deduction for adventitious substances, such as siliceous 

 matter and charcoal. The figures exhibit very slight differences, 

 snch as could not justify any important conclusions, were these 



