DEO 



JUEF 



or deficiency of aii . In the first case, 

 the process is called Eremacausis ; in 

 the second, Fermentation, which sec. 



DECIDUOUS. Parts which fall 

 ofl^, such as hairs, horns, leaves, &c. 



DECOCTION. Any mixture which 

 has been boiled. 



DECOMPOSITION. In chemis- 

 try, the separation of the parts of any 

 compound, whether mineral or or- 

 ganic. Electricity and heat are the 

 principal forces used by chemists for 

 this purpose, and they are capable of 

 disturbing most combinations. Chem- 

 ical affinity, or the attraction which 

 one form of matter has for another, 

 is also an agent of decomposition. 

 Thus oil of vitriol (sulphuric acid) has 

 a powerful attraction for water ; if 

 it be dropped on the human hand a 

 blister is instantly produced, and the 

 part blackens. This decomposition 

 is owing to the greater affinity of the 

 acid for water than the flesh of the 

 hand. In the same way some min- 

 erals act on each other, producing 

 change of composition, or decompo- 

 sing them. Decompositions may be 

 expected if one of the ingredients is 

 of a volatile or gaseous nature, or if 

 the agent added forms with one of 

 the original components a product 

 which is insoluble in water. Thus 

 sulphuric and oxalic acid decompose 

 every solution of lime, because they 

 form insoluble salts with lime. Car- 

 bonic acid, in its salts, is decomposed 

 by every fixed acid, because it is gas-- 

 eous. Lime, potash, and soda de- 

 compose most salts of ammonia, be- 

 cause the latter is volatile. 



DECOMPOSITION OF FORCES. 

 A problem in physics, in which it is 

 desired to know in how many differ- 

 ent directions several forces have 

 acted to produce a given result. 



DECOMPOSITION OF LIGHT. 

 The separation of a beam of light 

 by means of a prism of glass, into the 

 seven colours, red, orange, yellow, 

 green, blue, indigo, violet, which are 

 hence called the primary colours, 

 light being the result of their mix- 

 ture. 



DECORTICATION (from de,from, 

 and cortex, bark). Taking off the bark. 

 826 



Scraping the bark, and even partially 

 removing it during the active growth 

 (June), has been found to invigorate 

 trees. It is often resorted to in bark- 

 bound trees which bear little fruit. 

 Care must be taken not to wound the 

 new wood or expose the sap. 



DECOY. "A device by which 

 aquatic birds, chiefly ducks, are enti- 

 ced from a river or lake up a narrow, 

 winding canal or ditch, which, grad- 

 ually becoming narrower, at last ter- 

 minates under a cover of network, of 

 several yards in length. The birds 

 are enticed by the smoothness of the 

 turf on the margin of the canal, 

 which tempts them to leave the wa- 

 ter, and begin to dress their plumage. 

 When so engaged at some distance 

 up the canal, they are suddenly sur- 

 prised by the decoy man and his dogs, 

 who have been concealed behind a 

 fence of reeds ; and having again ta- 

 ken to the water, they are driven up 

 by the dogs till they enter within the 

 network which terminates the decoy, 

 and are then easily caught." 



DECREPITATION. A chemical 

 term signifying crackling, and used 

 to describe the sound made by nitre, 

 salt, sulphate of potash, and other 

 salts, when thrown into the fire. 



DECUMBENT. In botany, incli- 

 ned downward. 



DECURRENT. In botany, a leaf, 

 a part of the lamina of which is at- 

 tached to the stalk of the plant. 



DECUSSATE. To cross and in- 

 termingle, in anatomy. 



DEER. The common species is 

 the Ccrinis Virginianus of naturalists ; 

 it is diffused throughout the United 

 States as far north as Canada. The 

 moose (C. alces) is the largest spe- 

 cies of the deer; it inhabits swamps, 

 and is confined to the most northern 

 parts of the States, and to Canada. 

 The reindeer (C. tarandus) is remark- 

 able for its immense horns, its value 

 to the inhabitants of the highest lat- 

 itudes, docility, and abstemiousness. 

 It is rarely seen in the States except 

 in Maine. Some other species are 

 found far in the northwest. 



DEFLAGRATION. A chemical 

 term, meaning very rapid combustion, 



