The farmer, who during his former lease, had expended his capital in improving his land, if it were still in his own hands, would be rated for this new tax according to the new value which the land had acquired by its improvement, and this amount he would be obliged to pay during his lease, although his profits might thereby be reduced below the general rate of profits; for the capital which he has expended may be so incorporated with the land, that it cannot be removed from it.