83 



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crop had been removed. It is obvious that, if tho results at these 

 two periods are to be compared, we must first determine whether the 

 samples taken represent layers of equal depth and weight in the two 

 cases. Confining attention on the present occasion to the results 

 relating to the first 9 inches of depth, the following figures show the 

 average weight of dry mould per acre ; that is, of soil excluding 

 stones and moisture, calculated from the weight of the samples taken, 

 and from the results of the mechanical separation, and of the deter- 

 mination of moisture in the soils. For 18G5, tho calculations are 

 based on the results afforded by 80 samples, eight from each of ten 

 of the eleven plots, the eleventh being the one annually receiving 

 farmyard manure ; and for 1881 they are based on the results relating 

 to 114 samples, that is, six samples each from 19 plots, again 

 excluding the one with farmyard manure. 



Number of Samples. 



1865, 10 plots, 8 samples from eacli 

 1881, 19 plots, 6 samples from each 



Calculated 



dry Mould 



per Acre. 



lbs. 

 2,299,038 

 2,552,202 



ITU 



s 



Tho importance of taking samples of definite area and depth, and 

 of determining the weights, is here strikingly illustrated. Thus, it is 

 obvious that the samples analysed in 1881 represented, on the average, 

 almost exactly one-ninth more soil per acre than those analysed in 

 1865. In other words, if the samples of 1865 fairly represented 

 9 inches of depth in the average condition of consolidation of the soil, 

 those of 1881 represented 10 inches of soil in the same condition : 

 that is, they included 1 inch more of subsoil, with its much lower 

 percentage of nitrogen than the 9 inches above it. It may, of course, 

 be a question whether the condition of consolidation of the soil was 

 the more normal at the one period or at the other. It would, how- 

 ever, make scarcely any difFerence in the relation of the results to one 

 another at the two periods, whether the actually determined per- 

 centas-es of nitroeren in the 1865 samples were lowered, on the 

 assumption that they should have included 1 inch more of subsoil, or 

 whether the determined percentages in the 1881 samples are raised, 

 on the assumption that they contained 1 inch too much of subsoil. 

 We have concluded, from a consideration of all the facts afc command, 

 that the latter alternative is upon the whole the best. We adopt, 



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