DOD 



DOG 



be taken to produce the condensa- 

 tion. This is managed in the labora- 

 tory by keeping pieces of wet rag on 

 the tube, or by passing it through an- 

 other larger tube of metal which is 

 cooled by a stream of water. In lar- 

 ger operations, the still beak enters 

 another long tube, which winds sev- 

 eral times in a bucket of water, and 

 is thus kept cool, the water being oc- 

 casionally renewed. 



Distillation is employed to separate 

 alcohol, ether, vinegar, and other 

 products from mixtures ; to obtain 

 the essential oil of plants ; and when 

 much heat is used, to separate gas 

 from coal ; tar and vinegar from green 

 wood ; hartshorn from bones, whale- 

 bone shavings, &c. When a distilled 

 product is re-distilled, it is said to be 

 rectified. 



DITCH. A trench cut in the 

 ground, usually round the fences of a 

 field. Trenches of this kind are form- 

 ed ditferently in various localities, but 

 they should always be made so as to 

 keep the water in them as pure as 

 possible. 



DIURESIS (from 6ia, and ovpcG), to 

 make water). Excessive urination : 

 hence Diuretics, medicines causing 

 urination, as nitre, juniper berries, 

 turpentine, cubebs, &c. See Ball. 



DIVARICATE. To spread out 

 widely. 



DIVERGENT. Branches separa- 

 ted by an angle. 



DIVISIBILITY. In chemistry, the 

 extent to which pieces of matter may 

 be divided is extraordinary ; thus, in 

 gilding, the thickness of gold on a 

 surface is often as little as 110,000th 

 part of an inch. But matter is not 

 infinitely divisible. 



DOCK. Troublesome, long-root- 

 ed, perennial plants, of the genera 

 Rumcx, Tassilago, &c. See Weeds. 



DODDER. A weed consisting of 

 thread-like stems, which bind togeth- 

 er the plants among which it grows. 

 It is occasionally destructive to small 

 crops, such as flax. 



DODECAHEDRON (from (5u(5f/ca, 

 twelve, and iSpa, a .seat). A solid 

 of twelve sides. In crystallography 

 there are two varieties ; the rhombic 



and angular dodecahedron, according 

 to the figure of the sides. 



DODECANDRIA (from (5a»Wa, 

 twelve, and ai^r/p, male). The class of 

 plants containing twelve stamens. 

 See Botany. 



DOE. The female of the fallow 

 deer. 



DOG. A genus of animals ( Cams), 

 including innumerable varieties. The 

 farmer requires a good rat and ver- 

 min dog, of which the varieties of 

 terrier are the best ; a house-dog, as 

 the Newfoundland, bull-dog, or mas- 

 tiff; and herd-dogs, as the sheep- 

 dog, the Scotch sheep-dog, or the 

 Spanish shepherd's dog. The last is 

 said to be the most manageable and 

 trusty, as it is the strongest, being 

 nearly as large as a Newfoundland ; 

 but the instinct of the Scotch animal 

 cannot be readily surpassed. Hunting 

 and coursing dogs are merely useful 

 for pleasure, but of these the pointer 

 is an animal of rare instinct, and can 

 be taught to equal the best sheep- 

 dogs in caring for flocks. 



Fiff. 1 is the Scotch shepherd's dog, 

 or colly. Characters: ears partly 



Fie. 1 



erect, head rather pointed, shaggy 

 coat, and thick tail. To this animal 

 large flocks are safely intrusted with- 

 out any shepherd. He is also capable 

 of managing cattle with great nicety. 

 Fis^. 2, the English sheep-dog, is 

 His colour is usually white 



larger. 





^»**; 



and black, with half-pricked ears. He 

 is an excellent cattle and farm dog. 



Dogs should be kept clean and fed 

 with wholesome food, under which 

 circumstances they are very healthy. 

 Worming is an absurd and useless 

 custom. The mange in dogs is the 



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