824: PRESERVATION OF FOOD PRESERVATION OF WOOD enclosing in air-tight cans with exclusion of air, after the manner of canning fruits. 7. By cooking and pickling in vinegar, a common method of preserving oysters, lobsters, and fish. Cooking and seasoning, and covering with melted lard or olive oil, is a common method of preserving very small fish. (See SAEDINE.) 8. By refrigeration and freezing, a process now extensively practised in all civil- ized countries, fresh beef being carried from South America to all parts of the world, and in the United States from the Pacific to the At- lantic coast. The trade in frozen herring from the coast of Maine and the bay of Fundy has recently grown immensely. (See FEEEZIN&, ARTIFICIAL.) Milk is preserved by evaporating it to the consistency of thick sirup, in which condition it resists the motion of ferments ; or by reducing it to a solid state, and adding a portion of salt. (See MILK.) There are several special methods, having particular names, which might be classified under some of the above heads. Appert's method, introduced in France about 1810, for which he received a prize of 12,000 francs from the board of arts and manu- factures in Paris, and which was afterward patented in England and improved by Donkin, Hall, and Gamble, consists principally in cook- ing the meats at a temperature of about 240, and sealing in air-tight jars. The process has been further improved by McOall and co., who add a small quantity of sulphite of soda (12 grains to every pound of meat), to absorb traces of oxygen which may have been left. Still another improvement is the application of entrance and exit tubes, the exhaustion of air through these by an air pump, and subse- quently the passing through the can of nitro- gen gas to remove all oxygen, and then of a small quantity of sulphurous acid, and after this of nitrogen ; after which the can is hermet- ically sealed. The merit claimed for this pro- cess is that the meat may be preserved without cooking. The process of Prof. Morgan of Dub- lin consists in forcing into the aorta of the re- cently slaughtered animal, and thence through- out the capillary and venous system, a strong brine, containing a small portion of saltpetre, by which means the blood is forced out of the system at the same time that the meat is salt- ed. It may then be cut into pieces, and dried and smoked, or preserved in brine. One objec- tion to this process is that it washes out nutri- tive material. By Dr. Endemann's process the meat is cut into thin slices and dried in a cur- rent of warm air not exceeding 140 F. It may then be ground into powder, kept in air- tight cans, and used for making soup. M. Laujorrois has lately communicated to the French academy a method of preserving food by the use of fuchsine (aniline red, rosanilhie, or magenta). A vessel containing a solution of gelatine treated with a minute quantity of fuchsine 11 months before, and open to the air ever since, was exhibited, and was found in a perfect state of preservation. PRESERVATION OF WOOD. In its natural state the durability of wood depends upon the variety of tree from which it is taken, the time of felling, the manner of drying, and the conditions in which it is placed. Natural wood in deep fresh water will last for centu- ries, as it is not liable to attacks of worms as it is in sea water, and its depth of immersion preserves it from eremacausis. Alternate ex- posure to air and water, or continued expo- sure to air and moisture combined, is most favorable to the decay of wood, especially if accompanied by warmth ; but different kinds of wood have vastly different powers of re- sisting such influences. (See WOOD.) Pure woody fibre is much less affected by the action of air and moisture than when it contains starchy, gummy, and albuminous matter. If felled in winter, after the sap has been mostly converted into woody fibre, it is more durable than if felled in summer. Kiln drying is the ordinary method of preserving wood which is to be worked by the carpenter or cabinet maker, by which the water is eliminated, and the albuminous and gummy constituents hard- ened. The constituents of the sap may be removed by boiling the wood in water or sub- jecting it to the action of steam, alternate vac- uum exhaustion and injection, if desired, aid- ing in the process of removal. This mode of treatment is practised when it is desirable that the grain and color of the wood be pre- served. The constituents of the sap may also be changed by the action of chemicals, and these may be introduced by first exhausting the air and vapor from the pores of the wood and then letting into the receiver a strong so- lution of the preserving substance. In England several scores of patents have been issued for processes for the preservation of animal and vegetable substances, including timber, of which only four were in the last century, the earliest being in 1737. The first process for preserva- tion by chemicals which was extensively, ap- plied was that of Mr. Kyan, which was pat- ented in England in 1832, and some time after- ward introduced into the United States by the inventor. The wood was steeped in a solu- tion of corrosive sublimate, or it was placed in an exhausting cylinder and the solution forced in under atmospheric pressure. Its expensive- ness, however, and the difficulty of conducting it, have prevented this process, called kyani- zing, from being widely employed. Of the prep- arations now in use in England, that of Mr. J. Bethel, consisting of the oily mixtures obtain by a rough distillation of the tarry liquor of works, is considered as very efficient. A solu tion of pyrolignate of iron is also regarded a good preservative. Because of the presen of creosote in these liquors and its known anti septic property, the process is called ere ting, and is effected by the method of exhau tion and subsequent injection by intense pre ure (150 Ibs. or more to the square inch), whic is continued for 48 hours or longer. The pr
