966 SYRUP 



SWAIiliOW, ESCULENT (Hirundo esculenta). These birds construct the 

 edible nests which form so considerable a part of Chinese commerce. It is the Larvet 

 of the Japanese, the Salangana of some -writers on the Eastern Archipelago. The 

 nests are made of a particular species of sea-weed (see ALGJB), which the bird 

 macerates and bruises before it employs the material in layers, so as to form the 

 whitish gelatinous cup-shaped nests so much prized as delicacies by the Chinese. 



SWANS'-DOWN. There is a production of 500,000 puffs made annually from 

 about 7,000 swans' -down skins, imported into Britain. 



SWEEP-WASHER is the person who extracts from the sweepings, potsherds, 

 &c. of refineries of silver and gold, the small residuum of precious metal. 



SWEETMEATS. Any article prepared chiefly with sugar is so called. A con- 

 siderable number are described under CONFECTIONEBT. 

 SYCAMORE. The wood of the Acer pseudo-platanus. 



SYENITE is a crystalline rock, consisting of orthoclase-felspar and hornblende ; 

 but the term is also frequently applied to a mixture of hornblende, orthoclase, and 

 quartz. It takes its name from the city of Syene, in the Thebaicl, near the Cataracts 

 of the Nile, but the rock there is not a true syenite. It is an excellent building-stone, 

 and was imported from Egypt, by the Komans, for the architectural and statuary 

 decorations of their capital. Hornblende is the characteristic ingredient, and serves 

 to distinguish syenite from granite, with which it has been sometimes confounded. 

 The Egyptian Syenite, containing but little hornblende, with a good deal of quartz 

 and mica, approaches most nearly to granite. It is equally metalliferous with porphyry. 

 In the island of Cyprus, it is rich in copper ; and in Hungary, it contains many valuable 

 gold and silver mines. Syenite forms a considerable part of the Criffle, a hill in 

 Galloway. The so-called ' granites ' of Leicestershire more nearly approach syenites. 

 A careful study of the rocks of the Grooby, Markham, and Bardon Hill quarries, will 

 show a gradual change of the granitic rock, through syenite, into a greenstone-porphyry. 

 This stone is extensively used in the metropolis and other large towns for ' pitching ' 

 and paving. Much of the ' granite' of the Channel Islands, used in the metropolis 

 for road-metal, is a syenite, or at least a hornblendic or syenitic granite. 



SYIiVANITE, or Graphic Tellurium. A valuable ore of gold and silver, 

 found at Offenbanya in Transylvania, in narrow veins traversing porphyry, and 

 at Gold Hill, North Carolina. Its analysis byPetz gave : silver, 11-47 ; gold, 21'97; 

 tellurium, 39'97 ; lead, 0'25 ; copper, 076; antimony, 0'58 = total, lOO'OO. 



SYLVINE. Chloride of potassium ; a mineral formerly of great rarity, but 

 found of late years in abundance among the deposits of potash-salts, overlying the 

 rock-salt of Stassfurt in Prussian Saxony, and at Kaluscz in Galicia. Sylvine is an 

 important source of other salts of potassium. 



SYMBOIiS. Signs adopted by chemists to indicate the simple elements, or the 

 combinations of them, forming a compound body. A symbolic language has been 

 universally adopted by chemists, and the facilities it offers very strongly recommend 

 it. The symbols H, 0, S, C, stand respectively for hydrogen, oxygen, sulphur, and 

 carbon ; each elementary substance being represented by the initial letter of its Latin 

 name. When the initial letter of any two elements are similar, as, for example, 

 carbon, chlorine, and calcium the first and third, or second letters of the name are 

 taken, as Cl (Chlorine), Ca (Calcium). See ATOMIC WEIGHTS, for the symbols of all 

 the known elements. 



These symbols not only represent the element, but the relative quantities of it 

 which enters into combination. This is, of course, an arbitrary, though convenient 

 arrangement. The letters HO, for example, represent, not merely hydrogen and 

 oxygen, but 1 part of hydrogen and 8 parts of oxygen, which in combination re- 

 presents water. A figure placed on either of the right-hand corners of the symbol for 

 any Element indicates the number of atoms which enter into the combination spoken 

 of, as HO 2 represents 2 atoms of oxygen combined with 1 atom of hydrogen peroxide 

 of hydrogen. A figure placed on the left hand doubles all that follows it up to the 

 addition sign + or bracketed symbols : 2HO represents 2 atoms of water ; KO, 

 kalium or potassium and oxygen = potash; SO Z , sulphur and oxygen = sulphurous 

 acid ; KO,S0 3 represents sulphate of potash, but KO,2SO' indicates .Bz-sulphate of 

 potash. 



A combination of symbols representing a compound body constitutes a formula. 

 SYNTHESIS is a Greek word, which signifies ' combination,' and is applied to the 

 chemical action which unites dissimilar bodies into a uniform compound : as sulphuric 

 acid and lime into gypsum ; or chlorine and sodium into culinary salt. 



SYRUP is a solution of sugar and water. Cane-juice, concentrated to a density 

 of 1 -300, forma a syrup which does not ferment in the transport home from the 

 West Indies, and may be boiled and refined ut one step into superior sugar-loaves. 



