Milk, cheese, and butter : a practical handbook on their properties and the processes of their production, including a chapter on cream and the methods of its separation from milk / by John Oliver.

  • Oliver, John (Writer on dairy products)
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Milk, cheese, and butter : a practical handbook on their properties and the processes of their production, including a chapter on cream and the methods of its separation from milk / by John Oliver. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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    the bucket and the cord, presses towards the bottom of the bucket. This is therefore called centrifugal force {ccniri-fugal, flying from a centre). The water, by reason of its pressing outwards, becomes denser ; and its increase of density depends on its weight, its distance from the centre, and the speed at which it revolves. The boy finds it more difficult to hold the bucket when he lets the cord out to greater lengths, or swings it round him with greater speed. Proceeding on these facts, we find that there are definite relations between the force and the conditions described, and these relations are reduced to rules by which we can calculate the amount of the force, and in proportion to this the density also. This rule holds good when two substances of unequal density are together under the influence of the force. Cork has a less specific gravity than water, and if a body of that material was subjected to the same revolving motion, it would e.xert less centrifugal force than an equal body of water. If the boy puts a cork into his bucket of water, it will have the same tendency to fly away from him ; not, however, to anything like the same e.\tent as the water, but only in proportion to its much lower weight or gravity. Further illustration of these principles will occur in practical dairy work. Rocks and Soils.—Soils are simply the rocks forming the earth’s surface reduced to powder by natural forces, such as water, and cold and heat, which are always at work, though unnoticed, wearing down or splitting up the materials referred to. In the simplest relations there will be a gradual difference observed as the rock merges into what is called the sub-soil, and from this again into the surface soil. But there are many places where tillage has interfered with these relations; and others where soils, formed elsewhere, have been brought by air or water and laid upon or mixed with those natural to the spot. In any case, however, the rock materials form on an average 95 per cent, of the whole. The main ingredients of soils are clay, sand, and lime, in varying proportions,—forming sandy or clay soils when these predominate, sandy or clay loams as they approach a balance, and loams in still closer proportions ; and when carbonate of lime—CaCO^—is found up to a fifth of their total, forming marly or chalky, or, in higher propor- tions, calcareous soils. There are present also, though in small quantities, other substances more or less helpful or hurtful to vege- tation. The materials in general may be classified for our immediate purpose into soluble and insoluble substances, and since the latter form only a bed in which plants can grow, we may devote our attention to the former, upon which they feed. Among these may be found the following, viz.:—