186 CHYMISTRY APPLIED TO AGRICULTURE. 



sists in keeping them in dry places, where the temperature 

 will constantly be between 50° and 54° Fahrenheit ; the 

 third, in separating the fruits, so that they shall not come 

 in contact; I have seen apples preserved in this manner 

 eighteen months. It is necessary to be particular in selects 

 ing fruit for preservation ; that only should be taken which 

 is perfectly sound. 



Wood and other portions of vegetables, and various ani- 

 mal substances, are likewise preserved by drying ; .this pro- 

 cess increases their hardness and renders them less accessi- 

 ble to the action of air, insects, and other destructive agents. 



The process -of drying is not confined to preserving 

 fruits from decomposition : it furnishes the means of secur- 

 ing their juices unaltered for the formation of extracts ., of 

 them. 



When the juices of plants can be extracted by pressure 

 alone, it is only necessary to evaporate these juices at a due 

 degree of heat and in suitable vessels, till, being deprived 

 of all the water which retained them in a liquid state, they 

 are reduced to dryness. Evaporation, if continued for a 

 long time at the temperature of boiling water, changes these 

 juices a little ; the albumen, which is contained more or 

 less abundantly in all sweet fruits, is coagulated, and after 

 this they are no longer susceptible of undergoing the vinous 

 fermentation. 



The must of grapes, operated upon in this manner, fur- 

 nishes an extract called raisine, which is an article of 

 food both wholesome and agreeable, and which, when 

 soaked in water, decays without producing alcohol. The 

 fermentative power of this substance may, however, be re- 

 stored by mixing with it a little of the yeast of beer, as 

 this repairs the loss, which the juices had sustained by 

 heat during evaporation. 



All the juices obtained from sweet fruits may be convert- 

 ed into extracts, and thus furnish agreeable food : the qual- 

 ity of the extract varies according to the quantity of sugar 

 contained in the fruit, and the care taken in the operation : 

 when the juices are several times clarified, and evaporation 

 carried on in a water bath, care being taken to stir the 

 liquid to prev^ent its adhering to the sides, the color and taste 

 of the extract or jelly obtained is far superior to that pro- 

 cured without employing these precautions. 



The sweetest fruits, however, even the well ripened 

 grapes of the south, contain a portion of acid, which, 



