The Wealth of Nations by Part 1 Chapter 11 Page 244

price of butcher’s meat, the increase of the demand, and, in consequence of the improvement of the country, the diminution of the quantity which can be fed at little or no expense, raise, in the same manner, that of the produce of the dairy, of which the price naturally connects with that of butcher’s meat, or with the expense of feeding cattle. The increase of price pays for more labour, care, and cleanliness. The dairy becomes more worthy of the farmer’s attention, and the quality of its produce gradually improves. The price at last gets so high that it becomes worth while to employ some of the most fertile and best cultivated lands in feeding cattle merely for the purpose of the dairy; and when it has got to this height, it cannot well go higher.

If it did, more land would soon be turned to this