78 DISAPPEARANCE OF CARBONATE OF LIME IN SOIL. 



and heavy rate as would Lave given to the soil (by calculation) at 

 least three per cent, of calcareous earth, for the depth of five 

 inches. Only a small portion of the shelly matter was very finely 

 divided when applied. Since the application of the greater part 

 of this dressing (only one-fourth having been laid on in 1818), no 

 more than six years had passed before the following examinations 

 were made (at end of 1826) ; and the cultivation of five crops in 

 that time, three of which were horse-hoed, must have well mixed 

 the calcareous earth with the soil. Three careful examinations 

 gave the following results : 



No. 1. 100 grains yielded 7 J of coarse calcareous earth (fragments 

 of shells), 



And less than J of finely divided. 



8 



No. 2. 1000 grains yielded 5 of coarse, 



2 finely divided, 



No. 3. 1500 grains yielded 15 of coarse, 



2? finely divided. 



17} 



The specimens, No. 1 and No. 2, were obtained by taking hand- 

 fuls of soil from several places (four in one case, and twelve in the 

 other), mixing them well together, and then taking the samples 

 for trial from the two parcels. On such land, when not recently 

 ploughed, there will always be an over-proportion of the pieces of 

 shells on the surface, as the rains have settled the fine soil, and 

 left exposed the coarser matters. On this account, in making 

 these two selections, the upper half-inch was first thrown aside, and 

 the handful dug from below. No. 3 was taken from a spot, show- 

 ing a full average quantity of small fragments of shells, and in- 

 cluded the surface. I considered the three trials made as fairly as 

 possible, to give a general average. Small as is the proportion of 

 finely divided calcareous earth exhibited, it must have been in- 

 creased by rubbing some particles from the coarser fragments, in 

 the operation of separating them by a fine sieve. Indeed it may 

 be doubted whether any proportion remained very finely divided 

 or in other words, whether it had not been combined with acid, as 

 fast as it was so reduced. But without the benefit of this supposi- 

 tion, the finely divided calcareous earth in the three specimens 

 averaged only one ,and one-fourth grains to the thousand, which is 

 one twenty -fourth of the quantity laid on; and the total quantity 



