DUG 



DUR 



trived that, by executing certain move- 

 ments, very small quantities of electricity 

 communicated to a part of the apparatus 

 may be continually doubled, until it be- 

 comes perceptible by an electroscope. 



DRACO. The Dragon; a northern 

 constellation, consisting of eighty stars, 

 the principal of which is Rastaber. 



DRAUGHT OF WATER. The 

 depth to which the lowest point of a ship 

 sinks in water ; in ships of the largest 

 size the draught is nearly thirty feet. 



DRIFT. A term used in Navigation 

 to express the angle which the line of a 

 ship's motion makes with the nearest 

 meridian, when she drives with her side 

 to the wind, and is not governed by the 

 power of the helm ; and also the distance 

 which the ship drives on that line in a 

 storm. 



The drift of a current is its velocity; 

 the direction of a current is called its set. 



DROP. The smallest perceptible por- 

 tion of a liquid. It is of a globular form, 

 and thus illustrates the theory that the 

 molecular forces of all bodies are equally 

 exerted around the centre of their 

 masses. 



DROSO'METER (3p6<rop, dew, juerpoi/, 

 a measure). An instrument for mea- 

 suring the quantity of dew deposited 

 upon the surface of a body. 



DRUPE {drupcB, unripe olives). In 

 Botany, a pulpy fruit, without a valve or 

 outward opening, containing a bony nut, 

 as the cherry. 



DRY PILE. The name of a galvanic 

 apparatus, constructed with pairs of 

 metallic plates, separated by layers of 

 farinaceous paste mixed with common 

 salt. The name is inappropriate, as the 

 apparatus evidently owed its eflScacy to 

 the moisture of the paste. 



DRY ROT. A species of decay to 

 which wood is subject. The wood loses 

 all its cohesion, and becomes friable, and 

 fungi generally appear upon it ; but the 

 first destructive change is probably of a 

 chemical kind, allied to the action of fer- 

 mentation. 



DU'ALISM (duo, two). A system of 

 philosophy which refers all existence to 

 two ultimate principles. 



DU'BHE. A star of the first magni- 

 tude in the northern constellation Ursa 

 Maj r. 



DUCT, IN PLANTS. A membranous 

 tube with conical or rounded extremities, 

 and its sides marked with transverse 

 lines, rings, or bars; unlike the spiral 

 vessel, it is incapable of unrolling with- 

 113 



out breaking. The varieties are the 

 closed, the annular, the reticulated, and 

 the scalariform. 



DUCTI'LITY {duco, to draw). That 

 property of bodies by which they admit 

 of being drawn out into wire. Platinum 

 has been drawn into threads not much 

 larger than those of the spider's web, 

 and gold wire has been found so thin, 

 that 550 feet of it weighed only one 

 grain. 



DU'CTUS {duco, to lead). A duct or 

 tube which conveys away the secretion of 

 a gland. 



DU'MASINE. An empyreumatic oil, 

 obtained by rectifying acetone derived 

 from the acetates. 



DUMOSE {dumus, a bush or bramble). 

 The character of a shrub which is low 

 and much branched. 



DUNES or DOWNS. Low hills of 

 blown sand which skirt the shores of 

 Holland, England, Spain, and other coun- 

 tries. 



DUODECIMALS {duodecim, twelve). 

 An operation in Arithmetic, technically 

 called cross multiplication and squaring 

 of dimensions. Its object is to find the 

 contents of any surface or solid by mul- 

 tiplying together its linear dimensions. 



DUPLICATE RATIO. The compo- 

 sition of a ratio with itself once; thus, 

 the ratio of a^ to b^ is the duplicate of the 

 ratio of a to b. If there be three quan- 

 tities in continued proportion, the first 

 is to the third in the duplicate ratio of 

 the first to the second; thus, if a, b, c 

 be continual proportionals, that is, if 

 a '. b ] '. b '. c, then, a is to c m the du- 

 plicate ratio of a to 6. 



DUPLICATION OF THE CUBE. A 

 celebrated problem, proposed by the ora- 

 cle of Delos, viz. " to double the altar of 

 the God ;" this was tantamount to finding 

 the side of another cube of twice the solid 

 content. This problem, requiring the 

 solution of a cubic equation, was inca- 

 pable of solution by pure geometry, and 

 was, therefore, reduced by Hippocrates of 

 Chios to the insertion of two mean pro- 

 portionals between two given straight 

 lines. 



DU'PLO- {duplum, from duo, two, 

 plica, a fold). A Latin prefix, signifying 

 two-fold, as in duplo-carburet ; also, that 

 the organs of any body to which the term 

 is prefixed are twice as numerous or large 

 as those of some other body. 



DURA'MEN {durus, hard). The in- 

 terior, more deeply- coloured, and harder 

 portion of the trunk and branches of 



