A concentrated form of food, called _meat biscuit_, excited a considerable degree of attention in the Great Exhibition. It is formed by boiling down the fresh beef of Texas, and mixing into the strong beef-tea thus formed a certain proportion of the finest flour. The biscuit formed from these materials is so nutritive, that less than four ounces a day (mixed with warm water or not, according to circumstances) is sufficient food for a man in active service. It is very light and portable, and keeps perfectly well without change; hence it is admirably adapted to the provisioning of troops, ships, and overland expeditions. The manufacture is also of great importance to those countries in which cattle are superabundant, and are killed merely for the sake of their skins for the tanner, or their bones for the farmer, the flesh being actually thrown away. In some places, animals which we are accustomed to regard as valuable are so numerous that they are drowned by hundreds, merely to get rid of them, neither their skin, bones, nor flesh serving as a pretext for the wholesale slaughter. Milk has been preserved in the following manner: Fresh milk is reduced by boiling to one-half, and beaten up with yolk of eggs, in the proportion of eight eggs to every ten and a half quarts of milk. The whole is then placed on the fire for half an hour, and skimmed frequently; it is next strained and heated in a water-bath for two hours. It is stated that this milk will keep good for two years, and, if churned, would afford good butter. Cream may be preserved by boiling five measures down to four; then, after cooling and skimming, it is put into a bottle, corked down, luted, and kept in the boiling heat of a water-bath for half an hour. This, it is said, will keep two years. A much better method of preserving milk is that first pointed out by M. Dirchoff, the Russian chemist; namely, to solidify it by driving off the aqueous portion by a gentle heat. Specimens of consolidated milk were shown in the Great Exhibition; and it was stated that, after being dissolved in boiling water, and reproduced in the form of milk, the solution will keep pure for four or five days. As milk contains 873 parts of water in every 1000, it follows that 1000 parts of milk will yield by evaporation only 127 parts. 7. _Potting_ is only another contrivance for excluding animal substances from contact with air. Lean meat should be selected, cooked, and then reduced to a pulp by being beaten in a mortar, salt and spices being incorporated. The pulp is then rammed into jars, and preserved from the air by a thick coating of melted butter or lard poured over it.