Mildew, as may be seen under a microscope, is a species of fungus--a vegetable growing under certain conditions favourable to its development. If warp or cloth is sized or finished damp, then stored in a dry room for a considerable time, mildew may be expected, unless antiseptics have been used. An antiseptic is a substance tending to destroy vegetable life, and of antiseptics muriate of zinc and carbolic acid are the most suitable for sizing purposes. As chloride of magnesium does not prevent mildew, indeed, its use being rather favourable to the development of that evil, the name anti, or antiseptic, usually given to it is misleading. It is very important that a manufacturer should take every precaution to prevent mildew by the use of real antiseptics, especially when using such sizing materials as flour, tallow, or any other which readily mildews. It may be mentioned that the maker of the cloth is liable for any damage done in this respect, if the cause can be found in defective sizing, even though the growth may not be seen until the goods have arrived abroad. The before-mentioned chlorides are greatly dependent on the weather, and also on the situation of a shed, for their good weaving properties. In case of east winds, extremely dry or cold atmospheric conditions, or in a dry shed twist sized with magnesium, zinc or china clay, is rendered brittle first. Numerous other materials are used by a few manufacturers, but they do not require an extended notice. Dividing them into the four classes previously mentioned, we may refer to:--1st, maize, starch, tapioca, dextrin, and gum; 2nd, oils, compositions, spermaceti, curd soap, Irish moss, cocoanut oil; 3rd, French chalk, Epsom salts; whilst soda is used to prevent iron-mould, and blue to take away a yellow tinge from the size mixing. SIZE MIXING. Mixing is performed in becks--wooden tanks fitted with dashers, constantly revolving and stirring the mixture. To each beck pumps are attached so as to force the size to another beck to complete the mixing process; or, if the mixing is ready for use, to pump it to the size box of the slasher frame. A set of becks generally consists of four--two about 4 by 8 feet, and two each 4 feet square, while for heavy sizing a copper or copper-lined boiling pan is used. This latter is fixed at a higher level than the becks for convenience in transferring the boiled size to the becks.