SIP 



664 



8IU 



of a series of successive layers, concentric, 

 plane, or undulated, and nearly or quite 

 parallel. It appears under various forms, 

 stalactical, tuberose, reniform, globular, 

 cylindrical, &c. Pearl sinter isaquartzose 

 or siliceous mineral, brittle, porous, and 

 fibrous ; when compact it is reckoned a 

 variety of opal. 



SIN'CATE, Lat. *inuatu$, indented. Ap- 

 plied to leaves when they are deeply 

 scolloped, the lobes standing apart as if 

 part of the leaf were cut away. 



SIN'COCS, Lat. tinuosus. In the fine 

 arts, of an undulating form. 



SI'NBS (Latin). A bag ; a cavity or de- 

 pression ; a groove ; a bay of the sea. In 

 anatomy, the veins of the dura mater are 

 called sinuses, &c. In surgery, the name 

 sinus is given to a long, narrow, hollow 

 track, leading from some abscess, dis- 

 eased bone, &c. 



SI'PHON. 2<p*. A tube. In hydrau- 

 lics, a bent pipe used to draw off wine and 

 other liquors from vessels containing 

 them, without disturbing the sediment 

 which may be deposited, or where other 

 modes may not be applicable. The opera- 

 tion of the siphon is simple ; being filled 

 with water and the shorter leg im- 

 mersed in the liquid to be run off (as 

 shown in the figure), the atmosphere, 



acting continually upon the surface of the 

 fluid, will force a continuous stream 

 through the siphon, provided the high- 

 est point does not exceed 34 feet in the 

 case of water, and proportional heights 

 for other fluids corresponding to their 

 specific gravities. 



SIPHOUA'RIA. A genus of gasteropods 

 of the order Pectinibranchiata ; and family 

 Capuloida. Named from the animal being 

 furnished with a siphuncle or hydraulic 

 apparatus. 



SIPHO'NIA. 1. The generic name of the 

 elastic gum-tree (S. elastica), class Mo- 

 naecia ; order Monadelphia. It yields the 



gum-elastic. 2. A genus of sponge-like 



fossil exhibiting a tubular structure. 



SIPHONOSTOMA. The name of a family 

 of i/aruiucal crustaceans of the order 



Paeeilopoda, now divided into two tribes, 

 the Calagides, comprising Argtd* and 

 Caligus (fish-louse), and the Lerneiformet, 

 comprising Jhcheleitium and Xicothoe 

 (lobster-louse). Name from /> and 

 trrouAi, a siphon or sucker fulfilling the 

 functions of a mouth. 



SIPH'UNCLE, dim. of siphon. A hydrau- 

 lic apparatus belonging to chambered 

 shells, passing through the several cham- 

 bers, terminating in a large sac, which 

 surrounds the heart of the animal. Its 

 use appears to be to increase or diminish 

 the specific gravity, so that the animal 

 may rise or descend at pleasure. 



SI'KEN. 1. In antiquity, a goddess who 

 enticed men into her power by the charms 

 of music, and devoured them. A mermaid. 



2. The name given by Linnaeus to a 



genus of Batrachians, of which the S. 

 lacertina, which inhabits the rice swamps 

 of Carolina, is the best known species. It 

 attains a length of three feet; has four 

 toes on each foot, and the tail compressed 

 into an obtuse fin. It lives in the mud, 

 feeds on lumbrici, insects, &c. There are 



other two small species. 3. See MAN- 



ATCS. 



SIRI/NE. In acoustics, an instrument 

 for determining the velocity of aerial 

 vibration, corresponding to the different 

 pitches of musical sounds. 



SIRI'ASIS, Lat. from jo?, the cavity of 

 the fontanel. An inflammation of the 

 brain, said to be peculiar to children, and 

 attended with hollowness of the eyes and 

 depression of the fontanel. 



SIR'IUS, 2e//os, the Dog-star. A very 

 brilliant star of the first magnitude, in the 

 mouth of the constellation Can is Major or 

 the Great Dog. This is the brightest and 

 probably the nearest of the fixed stars. 



SIROC'CO (Ital.). ) - o rlROC 



SIROC'O (Span.). } See SclROC - 



SIS'TRCM, iriniv, to shake. A kind of 

 timbrel, used at the Egyptian festivals of 

 Isis. 



SISYM'BRICM. The Cress: a genus of 

 herbaceous plants. Tetradynamia Sili- 

 quosa. Name from eirvSos, fringed, be . 

 cause of its fringed roots. The commot 

 and the broad-leaved sisymbrium, the 

 water-cress and the fixweed, or herb 

 sophia, are British types. 



SIT'TA. The nuthatch : the name of a 

 genus of passerine birds, of the Tenuiros- 

 trine family. The beak is straight, pris- 

 matic, and pointed, and is employed in 

 perforating the bark of trees, in search of 

 larvae. 



SI'DK. The water- parsnip : a genus of 

 perennial plants. Pentandria Dio'tnii 

 Name from ma, to move, on account of 

 its agitation in water. There are fo-ir 

 British species. 



