DWA 



DYN 



contain a fibre capablr of unrolling. 

 They are marked with dots, bars, &c., 

 and are probably the channels in 

 which some part of the ascending sap 

 flows. 



DUMOSE (from dumus, a bush). 

 Bushy. 



DUNES. Hillocks of drift sand 

 found on the seacoast of New-Eng- 

 land and elsewhere. They are very 

 destructive to agriculture, and are to 

 be arrested only by growing long-root- 

 ed reed grasses, trees, &c., on them. 

 Species of Arundo and Elymus have 

 thus been made to arrest their ad- 

 vancement towards cultivated lands. 



DUNG. See Farm-yard Manure, 

 Night-soil. 



DUODENUM. The intestine im- 

 mediately next to the stomach. 



DURA MATER. The fibrous cov- 

 ering of the brain. 



DURAMEN. The heart wood. 



DURHAM CATTLE. See Cattle. 



DWARF TREES. The art of cul- 

 tivating fruit-trees of moderate or 

 dwarf size in the place of large, nat- 

 ural standards is an important point 

 in horticulture. Dwarfs are procured 

 by grafting on slow-growing, small 

 varieties, as the apple or pear on the 

 quince stock ; by raising seedlings in 

 pots, and transplanting into poor, bar- 

 ren soils, or by causing a branch to 

 take root and allowing it to fruit as 

 early as possible. Lopping off the 

 upright branches is the more common 

 method of hindering trees from grow- 

 ing too lofty. Fancy gardeners often 

 procure ornamental dwarfs of the or- 

 ange by grafting a cutting with flow- 

 er buds on a root and allowing it to 

 fruit. The Chinese are very curi- 

 ous in the cultivation of ornamental 

 dwarfs ; the following is the method 

 employed by them : 



" The extremity of a branch, two 

 or three feet in length, in a fruit or 

 flower bearing state — for example, 

 the points of the branches of a fir- 

 tree bearing cones, or of an elm bear- 

 ing blossom buds — being fixed on, a 

 ring of bark is taken olf at the point 

 where it is desired that the roots 

 should be produced. The space thus 

 laid bare is covered with a ball of 

 246 



moist clay, which is kept moist by 

 being covered with moss, which is 

 occasionally watered. In the course 

 of two or three months in some trees, 

 and of a year or two in others, roots 

 are protruded into the ball of clay. 

 The branch may then be cut off be- 

 low the part from whence the roots 

 have been protruded, and the branch 

 being planted in a pot of poor soil, 

 and kept sparingly supplied with wa- 

 ter, it will remain nearly in its pres- 

 ent state for many years, producing 

 leaves, and, perhaps, flowers, annual- 

 ly, but never shoots longer than a few 

 lines." 



DYEING. See Cotton Dyeing, and 

 the different colours. 



DYER'S BROOM. See Wood 

 Waxen. 



DYER'S WEED. Weld. 



DYKE. A low earthen wall ; an 

 embankment. In geology, a mass of 

 condensed mineral matter, such as 

 granite, porphyry, basalt, trap, &c., 

 found intersecting strata, and evi- 

 dently produced by injection, in a 

 molten condition, through the strata. 

 They have been forme l during vio- 

 lent earthquakes, am' are very im- 

 portant as forming an impervious 

 barrier to the drainage of land, and 

 giving rise to springs on hillsides. 



DYNAMICS (from dvvanic;, poiccr). 

 The science which examines the laws 

 and conditions of motion, in contra- 

 distinction to mechanics, which in- 

 vestigates the conditions of rest and 

 action of forces not producing mo- 

 tion. 



DYNAMOMETER (from 6vva/icc, 

 and juerpov, a measure). An instrument 

 for the purpose of measuring the 

 amount of strength or force exerted 

 in any draught, &c. In ascertaining 

 the draught for ploughs and other 

 agricultural implements, dynamome- 

 ters are now regularly introduced. 

 The commonest is Regnier's, consist- 

 ing of two semi-elliptical bars of steel 

 welded together at the ends, one of 

 which is affixed to the clevis of the 

 plough and the other to the hook of 

 the swinging trees. As draught is 

 made the springs are pulled closer 

 together, and set an index in motion 



