D I A 



C 73] 



D I C 



ing the position in which shells should be 

 held to ascertain the right from the left side, 

 &c. Perhaps, the most simple plan is, to 

 place the apex of any spiral shell towards 

 the eye with the mouth downwards ; dextral 

 shells will then be found to have their 

 aperture on the right side of the axis; 

 sinistral shells, on the contrary, will have 

 theirs on the left of the axis. 



DI'ABASE. The French name for green- 

 stone ; a trap- rock, composed of horn- 

 blende and feldspar. 



DIADE'LPHIA. (from dig and adeXtyog, 

 Gr.) The seventeenth class of plants in 

 the artificial system of Linnseus. The 

 stamens are united into two parcels at 

 the base. This class has papilionaceous 

 flowers and leguminous fruits. Familiar 

 specimens will be found in the garden 

 pea, bean, &c. &c. 



DIADE'LPHOUS. Having its stamens united 

 into two parcels at the base ; belonging to 

 the class Diadelphia. 



DIA'GONAL. (diaywviog, Gr. db angulo ad 

 angulum perductus : diagonius, Lat. dia- 

 gonal, Fr. diagonale, It.) A line reach- 

 ing from one angle to another, so as 

 to divide a parallelogram into equal parts. 

 Diagonals principally belong to quadrila- 

 teral figures. 



DIA'GONALLY. (diagonalement ', Fr. dia- 

 gonalemente, It.) In a diagonal direc- 

 tion. 



DI'ALLAGE. Schiller-spar ; a variety of 

 serpentine, or crystallized serpentine. 

 The colour of diallage is dark-green. 



DIA'METER. (^ta/zerpoe,Gr. diameter lineam 

 dimentiens, per medium secans: diame- 

 ter, Lat. diametre, Fr. diametro, It.) 

 A straight line passing through a centre, 

 and terminated both ways by the sides or 

 surface of a figure. 



DIAME'TRAL. ) (diametral, Fr. diame- 



DIAME'TRICAL. $ trale, It.) Describing 

 a diameter ; relating to the diameter. 



DIA'METRALLY. } (diametralement : , Fr. 



DIAMETRICALLY. { diametralmente, It.) 

 In a diametrical direction ; in direct oppo- 

 sition ; directly. 



DI'AMOND. (diamant, Fr. diamante, It. 

 da/ic, Gr. adamas, Lat.) The hardest 

 and most valuable of all the precious 

 stones. Strange as it may appear, dia- 

 mond consists of pure carbon. If the 

 best charcoal be burnt in oxygen, carbonic 

 acid gas is formed, the weight of which 

 is nearly equal to that of the charcoal 

 and the oxygen, there being a small re- 

 siduum of earthy ashes left after the com- 

 bustion ; but if, in like manner, a diamond 

 be burnt in oxygen, carbonic acid gas is 

 equally the result, though, in the latter 

 case, there is no residuum, and the car- 

 bonic acid gas obtained is precisely equal 

 in weight to the two elements, the oxygen 



and the diamond. Why, or how, it is 

 that the same elementary substance can, 

 with little or no addition, form two such 

 excessively dissimilar bodies as diamond 

 and charcoal, the former the hardest and 

 clearest body in nature, the latter a mere 

 black, soft, brittle mass, is a mystery be- 

 yond our finite powers to comprehend. 

 The primitive crystal of the diamond 

 is the regular octohedron, each triangular 

 facet of which is sometimes replaced by 

 six secondary triangles bounded by curved 

 lines ; so that the crystal becomes sphe- 

 roidal, with 48 facets. When rubbed, 

 the diamond shews positive electricity. 

 It reflects all the light falling on its pos- 

 terior surface at an angle of incidence 

 greater than 24 13', whence its great 

 brilliancy is derived. It is the natural 

 edge of the diamond only that has the 

 property of cutting glass, all artificially 

 formed edges will only tear or scratch it. 

 Diamonds are found of nearly every 

 shade of colour, those which are colourless 

 are deemed the most valuable. The largest 

 diamond known is said to be that which 

 belonged to the late Emperor of the Bra- 

 zils ; it is uncut, and weighs 1680 carats, 

 or 11 ounces 96 grains. This magnificent 

 gem would be worth, supposing the table 

 of rates to be applicable to stones above 

 a certain size, 5,6'45,000/., but the highest 

 price that has ever been given for a single 

 diamond is 150,000/. A diamond in the 

 possession of the Great Mogul is of the 

 size of half a hen's egg. The Pitt dia- 

 mond, now the property of the king of 

 the French, was sold for 100, OOO/. ; it 

 weighs 136 carats, or nearly 1 ounce. 



DI'AMOND-SHAPED. Leaves are so called 

 when approaching to a square, having 

 four sides, of which those opposite are 

 equal : the four angles are generally, two 

 obtuse, and two acute. 



DIA'NDRIA. (from dig, and v/)p, Gr.) 

 The second class of plants in Linnaeus' 

 artificial arrangement ; they have two 

 stamens. This is a very numerous class, 

 consisting of three orders, and compre- 

 hends all hermaphrodite flowers having 

 two stamens. 



DIA'NDRIAN. Having two stamens ; be- 

 longing to the class Diandria. 



DIAPHANE'ITY. (diaphaneite, Fr.) Trans- 

 parency. 



DIA'PHANOUS. (SiaQavrig, from SiatyaivM, 

 Gr. diaphane, Fr.) Which may be seen 

 through ; transparent ; pellucid. 



DI'APHRAGM. (Sia(ppayfia, Gr. dia- 

 phragma, Lat. diaphragms, Fr. dia- 

 fragma, It. ) A large transverse muscle, 

 which separates the chest from the belly ; 

 the midriff. 



DI'CERAS. (from Sig and Kepag, Gr.) 

 A genus of fossil shells discovered in 



L 



