28 DIASPOBE 



by it, such as cameos, intaglios, &c. There has been a discovery made of the peculiar 

 power of diamond dust upon steel ; it gives the finest edge to all kinds of cutlrrv. MM- I 

 threatened at one time to displace the hone of Hungary. Finely -powdered corundum, 

 however, now occupies its place. It is well known that in cutting a diamond, the 

 dust is placed on the teeth of the saw, to which it adheres. To this dust is to bo 

 attributed solely the power of man to make brilliant from rough diamonds. 



Diamond dust can be made by voltaic electricity but not economically. 



DIAMOND MICROSCOPES were first suggested by Dr. Goring, and have l^cn 

 well executed by Mr. Pritchard. Among the different crystalline forms of the 

 diamond, probably the octahedron and the cube are the only ones that will give a 

 single vision. It will, in many cases, be advisable to grind diamond lenses plano-con- 

 vex, both because this figure gives a low spherical aberration, and because it saves 

 the trouble of grinding one side of the gem. A -concave tool of cast iron, paved with 

 diamond powder, hammered into it by a hardened steel punch, was employed by Mr. 

 Pritchard. This ingenious artist succeeded in completing a double convex of equal 

 radii, of about ^th of an inch focus, bearing an aperture of ^th of an inch with dis- 

 tinctness upon opaque objects, and its entire diameter upon transparent ones. 



DIAMOND SPAR. A name given to corundum, as it is next to the diamond 

 the hardest known mineral. See CORUNDUM. 



DIAMOND TOOIiS. 1. The Glaziers' cl;r;:::ond is the natural diamond, so set 

 that one of its edges is brought to bear on the glass. 



The extreme point of any diamond will scratch glass, making a white streak ; but 

 when the rounded edge of a diamond is slid over a sheet of glass with but slight 

 pressure, it produces a cut, which is scarcely visible, but which readily extends through 

 the mass. 



Dr. Wollaston succeeded in giving to the ruby, topaz, and rock crystal forms similar 

 to those of the diamond, and with those he succeeded in cutting glass ; proving that 

 this useful property of the diamond depended on its form. Although the primitive 

 form of the diamond is that of a regular octahedron, the Duke de Bournon published 

 upwards of one hundred forms of crystallisation of the diamond. The irregular octa- 

 hedrons with round facets are those proper for glaziers' diamonds. 



Notwithstanding the hardness of the diamond, yet, in large glass works, as many as 

 one and two dozens are worn out every week : from being convex, they become rapidly 

 concave, and the cutting power is lost. 



2. Diamond drills are made of various shapes ; these are either found amongst im- 

 perfect diamonds, or, selected from fragments split off from good stones in their 

 manufacture for jewelling. 



For description of the diamond-mounted borers, used for rock-drilling, see BORING. 



DIAPER is the name of a kind of cloth, used chiefly for table-linen. It is known 

 among the French by the name of Toilefourre, and is ornamented with the most exten- 

 sive figures of any kind of tweeled cloth, excepting damask. The mounting of a loom 

 for working diaper is, in principle, much the same as a draw-loom, but the figures being 

 less extensive, the mounting is more simple, and is wrought entirely by the we.uvi.-r, 

 without the aid of any other person. As tweeled cloths, of any number of leaves, are 

 only interwoven at those intervals when one of the leaves is raised, the woof above and 

 the warp below are kept floating or flushed, until the intersection takes place. Of con- 

 sequence the floating yarn above appears across the fabric, and that below longitudi- 

 nally. This property of tweeled cloths is applied to form the ornamental figures of 

 all kinds of tweeled goods, merely by reversing the floating yarn when necessary. In 

 the simpler patterns this is effected by a few additional leaves of treddlos ; but when 

 the range of pattern becomes too great to render this convenient, an apparatus calli-.l ;i 

 black harness is employed, and the cloth woven with this mounting is called diajuT. 

 Diapers are generally five-leaf tweels, that is to say, every warp floats under four 

 threads of woof, and is raised, and of course interwoven with the fifth. This is dono 

 either successively, forming diagonals at 45 upon the cloth, or by intervals of two 

 threads, which is called the broken tweel. The latter is generally, if not universally, 

 adopted in the manufacture of diaper. The reason of preferring the broken to tho 

 regular tweel, where ornaments are to bo formed, is very obvious. The whole depend- 

 ing upon reversed flushing, to give the appearance of oblique or diagonal lines through 

 either, would destroy much of the effect, and materially injure the beauty of tho fabric. 

 The broken tweel, on the contrary, restores to tie tweeled cloth a great similarity of 

 appearance to plain or alternately interwoven fabrics, and at tho same time pr< 

 the facility of producing ornaments by reversing tho flushing. 



DIAPHANOUS. Transparent to light. 



DIASPORE. A native hydrate of alumina, frequently found with emery and 

 corundum. It occurs in Asia Minor ; in tho Grecian Archipelago; at Schemuitz, in 

 Hungary ; and in Chester Co., Pennsylvania. 



