DIA 



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DIA 



DIA.I/LINQ-SPHKRE, an instrument usu- 

 ally made of brass, with several semi- 

 circles sliding over each other on a move- 

 able horizon, used to demonstrate the 

 nature of spherical triangles, and to give 

 the true idea of the methods of construct- 

 ing dials on all sorts of planes. 



DIAL'LAGE. In mineralogy, a dark- 

 green variety of crystallised serpentine, 

 thus named from J<*AXay*j, difference, in 

 allusion to the difference of lustre be- 

 tween its natural joints. Diallage is the 

 Verde di Corsica duro of artists, by whom 

 it is fashioned into ring-stones, snuff- 

 boxes, &c. In the rock it is called gabbro; 

 it ranks as a species of the genus Schiller- 

 spar, is named smaragdite by Saussure, 

 and euphotide by others. 



DIAI/YSIS, SiaXwKi a loosening (xvca, 

 to dissolve). 1. In grammar, a mark or 

 character consisting of two points placed 

 over one of two vowels to dissolve a diph- 

 thong, or to show that the two vowels 

 arc to be separated in pronunciation, as 



afirial. 2. In rhetoric, a figure of speech 



in which several words are placed toge- 

 ther without the aid of a conjunction, as 

 reni, vidi, vici. 3. In medicine, relaxa- 

 tion or weakness of the limbs. 



DIAM'ETER, from S;a, through, and 

 jt*T|oi, to measure ; a line which passing 

 through the centre of a circle or other 

 curvilinear nature divides it or its respec- 

 tive ordinates into two equal parts. In 

 conic sections, the line AB is called the 

 conjugate diameter, and the line C D is 



the transverse diameter. In architecture, 

 the measure across the lowest part of the 

 shaft of a column, which is usually di- 

 vided into sixty parts, called minutes, and 

 forms a scale for the measurement of the 

 other parts of the order. 



DIAMOND, a condensed and usually 

 crystallised form of carbon ranked as the 

 most beautiful and valuable, as it is the 

 hardest, of the precious stones, formerly 

 called adamant. Colours white and grey, 

 sometimes red, brown, yellow, green, and 

 rarely blue and black. The white is the 

 most valued ; when transparent and pure 

 it is said to be of the first water. When 

 cut it exhibits a beautiful play of colours 

 in the sun-beam. It has only been found 

 as yet within the tropics (in some parts 

 of India, in Borneo, and in Brazil), in di- 

 luvial gravel, and among conglomerate 

 rocks called cascalho, in Brazil, on which 

 it uay be said Europe depends at present 



for diamonds. The primitive form is the 

 regular octahedron, but each triangular 

 facet is sometimes replaced by six secon- 

 dary triangles bounded by curved lines, 

 so that the crystal becomes spheroidal 

 with 48 facets. Its brilliancy depends on 

 its property of reflecting all the light 

 which falls on its posterior surface at an 

 angle of incidence greater than 24 13' 

 only. The natural edges of the crystal 

 cut glass, artificial edges only scratch 

 it. The weight and consequently the 

 value of the diamond is estimated in 

 carats ; and the price of one diamond as 

 compared with another of equal purity 

 is as the square of the respective weights. 

 The largest diamond known is that in 

 the possession of the Queen of Portugal. 

 It is uncut, and weighs 1C80 carats, or II 

 oz. 96 grs. ; supposing therefore the table 

 of rates to be applicable to this diamond, 

 it is worth 1680 9 X 2/. =5,644 ,80C., but the 

 highest price ever paid for a diamond 

 was 150,OOOZ. A rough diamond is one as 

 it comes from the mines. A brilliant dia- 

 mond is one which is cut into facets both 

 at top and bottom. A rose diamond is one 

 which is quite flat beneath, with its upper 

 part cut into numerous facets, usually tri- 

 angles. A table diamond is one cut with 

 a large square face on top, encompassed 

 by four lesser ones. Diamond powder is 

 used for cutting, engraving and polishing 

 hard stones. The glazier's diamond, used 

 for cutting glass, is a small point of a 

 natural crystal of the diamond, set in a 

 socket of steel, lead, or silver. It is also 

 of late used by engravers to draw lines 

 which are to be deepened by aqua fortis 

 (dilute nitric acid). The term diamond is 

 used by heralds to express the black co- 

 lour in the achievements of peernge, and 

 the same name is given popularly to the 

 figure otherwise called a rhombus. 



DI'AMOND-SHAPED. Leaves are so called 

 when they approach in form to a square, 

 or resemble the figure of the diamond as 

 painted on cards. 



DIA'NA. 1. The moon. A name formerly 

 given to silver from its white shining 



appearance. 2. The goddess of hunting , 



twin sister of Apollo. 



DIA'NA, TREE OF, a name given to the 

 crystallised silver which is disengaged 

 when mercury is put into a solution of 

 nitrate of silver. 



DIAN'DRIA, from $i;, twice, and a.\v^, 

 a man. The second class of plants in the 

 Linnaean sexual system, comprising such 

 as have hermaphrodite flowers with two 

 stamens. 



DIAN'THCS, the pink. A genus of about 

 70 species, mostly hardy perennials. De- 

 candria Digynia. Name from A<? , Jove, 

 and etvOos , a flower, in allusion to the ele- 

 gance and fragrance of the flower. Th 

 T 2 



