Diamagnetism

(Magnet.) Dr. Faraday was the first (1845) to show that the magnetism of bodies was manifested in two ways-either in being attracted by the magnet, as iron; or in being repelled, like bismuth. When a needle or slender rod of iron is suspended between the poles of a magnet (Fig. 809), being attracted by them, it takes up a position of rest on the line ab, joining the two poles. When a substance behaves itself in this manner, it is said by Faraday to be paramagnetic, and to place itself axially, ab being the axis. A rod of bismuth, on the other hand, being repelled by the poles of the magnet, comes to rest in the line cd, at right angles to ab. Bismuth, and the like substances, he calls diamagnetic, and they are said to place themselves equatorially, ed being the equator. These terms, being both definite and graphic, have been universally adopted. Magnetic is the term used by Faraday to indicate magnetism of either sort, although in general language it is understood to refer to paramagnetic bodies, such as iron, . Paramagnetic bodies, then, are those Diam'etral, a. Diametrical; relating to a diameter; as, a diametral plane. one of 288 carats was found on Vaal river, and since then much larger ones have been found. The art of outting and polishing D. was discovered in 1456, by Louis van Berquen, a citizen of Bruges, who found that by rubbing two D. together, their surfaces might be abraded. At the present time diamond-cutting is principally carried on by Jews at Amsterdam. They are cut chiefly into two forms, called bril liants, and rose - dia monds, or rosettes, and sometimes into what are called, from their flat surface, table-diamonds. The brilliant form, which has from 56 to 64 facets, was first introduced by Cardinal Mazarin, in 1650. It is especially calculated to bring out the lustre and refractive powers of the gem. Thus, a well IMG:content-0600.png:[merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small] cut brilliant, held 1, regent; 2, great duke; 3, 4, vertical in a beam of light, reflects nearly the whole of the light which falls upon it. and lateral sppearance of the brilliant diamond; 5, vertical appearance of rose-cut diamonds; 6, 7, the table-cut diamond. throwing it out and refracting it in colored rays through the facets in front. With the exception of one small point of light through the collet , the brilliant forms an opaque shadow on a screen. Until recent years the largest known D. was that mentioned by Tavernier as belonging to the Great Mogul. It was found in 1850 in Golconda; and is said to have originally weighed 793 carats. Among the crown-jewels of Ru ia is the Orlow or Orloff D. , weighing 194 carats; it is of the size of a pigeon's egg, and was purloined from a Brahmin i cal idol by a French soldier; it pa ed through several hands, and was ultimately bought by the Empre Catharine for the sum of $450,000 and an annuity of $230,000. One of the most perfect D. hitherto found is a brilliant brought from India by a gentleman of the name of Pitt (hence called the Pitt Diamond ), who sold it to the regent duke of Orleans for $625,000. It weighs 1364 carats (430-55 grains). Another very celebrated D. is the Koh-i-no or (mountain of light), which became the property of the Queen of England on the annexation of the Punjaub, in 1850. It then weighed 186 carats, but it has been since re-cut, and reduced to 1034 carats. A D. known as the Excelsior, weighing 971 carats, has been found in the South African mines. D. are inflammable when heated red-hot and plunged into an atmosphere of oxygen, burning with a steady light, and giving rise to pure carbonic acid. The D. is not perfectly pure carbon, combustion leaving a small residue containing silica and iron. Its sp. gr. is about 3:34. It was first found to consist of carbon by Lavoisier, in 1775-6. The mines of Brazil yield yearly about $2,000,000; Africa not le than $20,000,000, but the character of the African stones is, as a rule, inferior to those of Brazil and India. ( Geom .) A figure, thus,; otherwise called rhombus , and lozenge . -One of the four suits of playing-cards, bearing the figure of a diamond or lozenge, in vermilion. of ammonia (N2Hg), in which the diatomic ethylene replaces two atoms of hydrogen. Such bases, formed upon the double ammonia type, are called diamines , while those which correspond to a simple atom of ammonia are called mon amines. The base above mentioned is named ethylene - diamine . The diamines, like the double atom of ammonia from which they are derived, are capable of combining with two equivalents of hydrochloric or any similar acid, which is implied by stating that they are diacid .