MECHANICS AND USEFUL ABTS. 55 



hermetically closed. M. Appert has improved this process in placing 

 the prepared vessels in a closed boiler, by which means he raises the 

 temperature (by pressure) to 234., effecting thus the same purpose 

 more rapidly and economically. To give you an idea of the extent 

 of this tra'le, I may state that M. Appert prepared over 500,000 pounds 

 of meat for the French army in the Crimea. I am aware that many 

 modifications have been applied to this process, but I shall only mention 

 that of Mr. G. McAll, who adJs to the previous principle of preservation 

 a small quantity of sulphate of soda, well known to be a powerful 

 antiseptic. 



The preservation of animal and vegetable substances by the exclu- 

 sion of air and cryptogamic sporules-is also effected by other methods 

 than those above described ; for instance, they are embedded in oil, or 

 in glycerine, or in saccharine sirups. 



It has also been proposed to protect animal matters by covering 

 their external surfaces with coatings impermeable to air. Two of 

 the most" recent are the following : M. Pelletier has proposed to 

 cover the animal matter with a layer of gum, then immerse it in ace- 

 tate of alumina, and, lastly, in a solution of gelatine, allowing the 

 whole to dry on the surface of the animal matter. The characteristic 

 of this method is the use of acetate of alumina, which is not only a 

 powerful antiseptic, but also forms an insoluble compound with gela- 

 tine, thus protecting the animal matter from external injury. M. 

 Pagliari has lately introduced a method which is stated to give very 

 good results. It consists in boiling benzoin resin in a solution of 

 alum, immersing the animal matter in the solution, and driving off 

 the excess of moisture by a current of hot air, which leaves the above 

 antiseptics on the animal matter, 



By Smoke and Carbolic Acid. It is scarcely necessary to men- 

 tion the old method of using smoke arising from the combustion of 

 various kinds of wood, except to state that in this case it is the creo- 

 sote and pyroligneous acids which are the preservative agents. The 

 preservation of animal matter by a very similar action is effected by 

 the use of carbolic acid, a product obtained from coal tar. It is 

 much to be regretted that this substance, which is the most powerful 

 antiseptic known, cannot be made available for the preservation' of 

 food, but there can be no doubt that, for the preservation of organic 

 substances intended for use in arts and manufactures, no cheaper or 

 more effective material can be found. For example, I have ascer- 

 tained that one part of carbolic acid added to five thousand parts of 

 a strong solution of glue will keep it perfectly sweet for at least two 

 years, and probably for an indefinite period. Also, if hides or skins 

 are immersed for 24: hours in a solution of one part of carbolic acid 

 to 50 of water, and then dried in the air, they will remain quite sweet. 

 In fact, hides and bones so prepared have been safely imported 

 from Monte Video. From these facts, and many others with which I 

 am acquainted, I firmly believe that this substance is destined within 

 a few years to be largely used as an antiseptic and disinfectant. 



By Salt and Heat. I need hardly speak of the power of chloride 

 of sodium, or common salt, in preserving animal matters, and it is 

 highly probable that the process of Mr. Morgan of Dublin (described 

 in the preceding article, Ed.) is likely to be of great service. At 



