In taking leave of the poultry-yard we are reminded of the dairy, and of the large establishments required to fill the milk-jugs of London. There are at the present moment, as near as we can learn, 20,000 cows in the metropolitan and suburban dairies, some of which number 500 cows apiece. Even these gigantic establishments have been occasionally exceeded, and one individual, several years ago, possessed 1,500 milkers--a fact fatal to the popular superstition, that notwithstanding many attempts, no dairyman could ever muster more than 999. The terrible ravages of pleuro-pneumonia, which many believe to be a contagious disease, have cured the passion for such extensive herds. The larger dairies of the metropolis are on the whole admirably managed, and the cows luxuriate in airy outhouses, but the smaller owners are often confined for space, and the animals are sometimes cooped in sheds, placed in tiers one above another. The country dairymaid laughs at the ignorance which the Londoner betrays of rural matters when on a visit to her master, but she would be perplexed in her turn if told that in the capital they fed the cows chiefly upon brewers' grains, and milked them on the _second story_? A few years since Mr. Rugg appalled the town, which had forgotten Matthew Bramble, Esq., and the "New Bath Guide," by detailing a nauseous process which he affirmed was in use among cunning milkmen for the adulteration of their milk. There was, however, a great deal of exaggeration in the account, and Dr. Hassell, whose analysis of various articles of food in the _Lancet_ are widely known, states that the "iron-tailed cow" is the main agent employed in the fraud, and that the only colouring matter he has been enabled to discover is annatto. Nearly all the cream goes to the West-End; and one dairyman living at Islington informed us that he made 1,200_l._ a year by the trade he carried on in that single article with the fashionable part of the town. It must be evident, upon the least consideration, that the London and suburban dairies alone could not supply the metropolis. If each of the 20,000 cows give on the average twelve quarts a day, the sum total would only be 240,000 quarts. If we suppose this quantity to be increased by the exhaustless "iron-tailed cow," of which Dr. Hassell speaks, to 300,000 quarts, the allowance to each individual of the two millions and a quarter of population would be little more than a quarter of a pint. This is clearly below the exigencies of the tea-table, the nursery, and the kitchen, and we do not think we shall make an overestimate if we assume that half as much again is daily consumed. Here again the railway, which in some cases brings milk from as far as eighty miles, makes up the deficiency. The Eastern Counties line conveyed in 1853 to London, 3,174,179 quarts, the North-Western 144,000 quarts, the Great Western 23,400 quarts, the Brighton and South Coast 100 tons, and