The analyses of butter show a very varying proportion of oleine and margarine fats: summer butter usually contains of oleine sixty and margarine forty per cent., whilst in winter butter these proportions are reversed, being forty of oleine to sixty of margarine. By ordinary treatment the quantity of butter during winter is markedly inferior. The common materials for dairy cows in winter are straw with turnips or mangel, hay alone, or hay with mangel. If we examine these materials, we find them deficient in oil, or in starch, sugar, etc. If a cow consume two stones or twenty-eight pounds of hay a day, which is probably more than she can be induced to eat on an average, it will be equal in dry material to more than one hundred pounds of young grass, which will also satisfy a cow. That one hundred pounds of young grass will yield more butter, will scarcely admit of a doubt. The twenty-eight pounds of hay will be equal in albuminous matter and in oil to the one hundred pounds of grass; but in the element of starch, sugar, etc., there is a marked difference. During the growth of the plant, the starch and sugar are converted into woody fibre, in which form they are scarcely digestible or available for respiration. It seems, then, not improbable that, when a cow is supplied with hay only, she will consume some portion of the oleine oil for respiration, and yield a less quantity of butter poorer in oleine. If you assume summer butter to contain of oleine, 60 per cent. If you assume summer butter to contain of margarine, 40 “ “ --- 100 “ “ If the cow consume of the oleine, 36 “ “ --- The quantity of butter will be reduced from 100 to 64 “ “ And the proportions will then be, of oleine, 40 “ “ And the proportions will then be, of margarine, 60 “ “ --- 100 “ “ If you supply turnips or mangel with hay, the cow will consume less of hay; you thereby substitute a material richer in sugar, etc., and poorer in oil. Each of these materials, in the quantity a cow can consume, is deficient in the supply of albumen necessary to keep up the condition of an animal giving a full yield of milk. To effect this, recourse must be had to artificial or concentrated substances of food, rich in albuminous matter.