SAG 



S AI 



RUTA'CE^. The Rue tribe of di- 

 cotyledonous plants. Herbaceous plants, 

 with leaves alternate, dotted ; flowers 

 symmetrical; petals alternate with the 

 divisions of the calyx; stamens hypo- 



gynous ; ovarium entire, celled ; fruit 

 capsular. 



RU'TILE {rutilue, red). Titan-schorl. 

 Native oxide of titanium. 



S 



SAC of the EMBRYO. The name 

 given by A. Brongniart to a fifth mem- 

 brane which sometimes occurs in the 

 ovule of plants. Mirbel calls this the 

 quintine, Malpighi the vesicula amnios, 

 and R. Brown the additional membrane. 



SA'CCHARINE MATTER {saccha- 

 rum, sugar). That portion of vegetable 

 substances which is sweet to the taste, or 

 which is capable of becoming sweet 

 under certain circumstances, or by cer- 

 tain manipulations. This, when suffi- 

 ciently fluid, readily enters into vinous 

 fermentation, emits carbonic acid gas, 

 becomes of less specific gravity, and the 

 product is a vinous liquor. See Alcohol. 



SA'CCHAROID ((raKxap, sugar, eldov, 

 likeness). Saccharine. A term applied 

 in Geology to a stone which has the tex- 

 ture of sugar, 



SACCHARO'METER {aaKxapov, 

 sugar, fxerpov, a measure). Literally, 

 a measurer of sugar ; an instrument em- 

 ployed in the operations of brewing and 

 of making sugar, its intention being to 

 indicate the density of the liquid ex- 

 tracted from malt and of that from the 

 sugar cane. It acts on the same prin- 

 ciple as the lactometer and the hydro- 

 meter, and such instruments are some- 

 times comprehended under the general 

 term areometer or gravimeter. 



SAFETY-LAMP. An instrument in- 

 vented by Davy for preventing the ex- 

 plosion of fire-damp in mines. It consists 

 of a lamp completely surrounded by a 

 cage of fine wire-gauze, through which 

 the explosive mixture cannot be fired. 

 So soon as the gas is inflamed within the 

 gauze, the miner is thereby admonished 

 to retire, lest the intense heat of the 

 flame should oxidise the metal, which 

 would then fall to pieces. 



SAFETY-VALVE. A valve fitted to 

 an opening in a boiler, and loaded with a 

 weight sufficient to withstand the elastic 

 pressure of the steam until it rise to a 

 certain degree, when it would be forced 

 out, and thus prevent the boiler from 

 bursting. 



SAGITTA. The Arrow; a northern 

 292 



constellation, consisting of eighteen 

 stars. 



SAGITTA'RIUS. The Archer; the 

 ninth of the Zodiacal signs, consisting of 

 69 stars. It denotes the third month of 

 spring, and extends from the 20th of 

 May to the 20th of June. In the Egyp- 

 tian zodiac the animal is figured with the 

 body of a quadruped and with a double 

 head, one of a lion, the other of an armed 

 man about to discharge an arrow ; it 

 seems to drive forward the animals which 

 precede it, and to check those which fol- 

 low ; every thing indicates that it will 

 soon reach the goal towards which it is 

 tendiufr, and that its course is on the 

 point of terminating. 



SAH'LITE. A variety of augite, in 

 which the magnesia is only in part re- 

 placed by protoxide of iron. Berzelius 

 calls it malacolite. It occurs in the sil- 

 ver mine of Sahla in Sweden. 



SAILING, or the SAILINGS. These 

 terms are applied to the different ways in 

 which the path of a ship at sea and the 

 variations of its geographical positions 

 are represented on paper. They are also 

 occasionally applied to the rules by 

 which, in particular circumstances, a 

 ship's place and its motion are com- 

 puted. 



1. Plane Sailing. This consists in re- 

 presenting the line of a ship's course or 

 way, for a given time, with the diffierence 

 between the latitudes and between the 

 longitudes of the two extreme points of 

 such course by the three sides of a right- 

 angled plane triangle, of which the dis- 

 tance actually sailed is the hypotenuse ; 

 the spaces on all the lines being ex- 

 pressed in nautical miles or equatorial 

 minutes of a degree, as if the earth 

 were a plane surface and the terres- 

 trial meridians and parallels of lati- 

 tude were straight lines respectively 

 parallel to each other. 



2. Middle-latitude sailing. This term 

 and that of globular sailing have been 

 briefly explained in their alphabetical 

 positions. The latter is a general term 

 for several modes of sailing, in which the 



