TIN 



TOI 



TIDES. A term applied to the pe- 

 riodic rising and falling of the ocean, 

 caused chiefly by the attraction of the 

 moon, but partly by that of the sun. 

 The sea flows, or rises, as often as the 

 moon passes the meridian, both the arc 

 above, and the arc below the horizon ; 

 and it ebhs, or falls, as often as she passes 

 the horizon, both east and west. When 

 the moon is in the first and third quarter, 

 i. e.,when she is new and when she is full, 

 or, in other words, when she is in con- 

 junction or in opposition, the tides are 

 high and swift, and are called spring- 

 tides ; when she is in the second, and last 

 quarter, i. e., when she is a half-moon, 

 or in her quadratures, the tides are lower 

 and slower, and are called neap-tides. 



TILE ORE. A sub-species of octo- 

 hedral red copper ore. An earthy variety 

 occurs massive and incrusting copper 

 pyrites ; the indurated variety is an inti- 

 mate combination of red copper ore and 

 brown iron ochre. 



TILGATE BEDS. The name given 

 by Dr. Mantell to a portion of the great 

 series of strata in the Weald of Kent and 

 Sussex, interposed between the green- 

 sands and the Portland oolite. 



TIME. A certain measure of dura- 

 tion, depending upon the motion of the 

 heavenly bodies, 



1. Equal or mean time, is that which 

 is reckoned by a clock, supposed to indi- 

 cate exactly 24 hours, from 12 o'clock 

 on one day, to 12 o'clock on the next day. 



2. Apparent time, is that which is 

 measured by the apparent motioji of the 

 sun in the heavens, as indicated by a 

 meridian line, or sun-dial. 



3. Sidereal time is that portion of a 

 sidereal day which has elapsed since the 

 transit of the first point of Aries, and 

 represents at any moment the right 

 ascension of any object which is then on 

 the meridian. 



4. Astronomical time of day is the 

 time past mean noon of the day, and is 

 reckoned on to twenty-four hours in 

 mean time. 



5. Civil time is mean time adapted to 

 the purposes of civil life. The civil day 

 commences at midnight, and is divided 

 into twelve hours marked a.m. or ante 

 meridian, and twelve marked p.m. or 

 post meridian. 



TIN. Stannum. A white metal ob- 

 tained from the peroxide, or common 

 ore, called stream-tin. The purer por- 

 tion of the metal thus obtained, is called 

 grain tin, the other portion ordinary tin 



or block tin. The metal is found asso- 

 ciated with sulphur and copper, consti- 

 tuting tin pyrites ; when combined with 

 oxide of iron and silex, it is called tin- 

 stone and wood-tin. The protoxide and 

 the peroxide are named, respectively, 

 the stannous and the stannic oxide. 



TIN-FOIL. An alloy composed chiefly 

 of tin, with a small portion of lead, and 

 sold in the form of a leaf of about the 

 1-lOOOth part of an inch in thickness. 



TINCAL. Crude borax, as it is im- 

 ported from the East Indies, in yellow 

 greasy crystals. When purified, it con- 

 stitutes the refined borax of commerce. 



TI'NEIDaE {tinea, a moth). A 

 family of Lepidopterous insects, consist- 

 ing of small moths, which infest woollen 

 stuffs and furs, upon which their larvae 

 feed. 



TIPU'LID^. A family of dipterous 

 insects, belonging to the section Nemo- 

 cera, and typified by the species com- 

 monly called Harry-long-legs. 



TISSUE. A web, or web-like struc- 

 ture, constituting the elementary struc- 

 tures of animals and of plants. 



TITAN-SHORL. Rutile. Native 

 oxide of titanium, a mineral comprising 

 the reticulated variety with golden var- 

 nish, from Moutier, near the Montblanc ; 

 acicular and capillary crystals of rutile 

 in rock crystal, from Brazil, &c. 



TITANI'FEROUS CERITE. A 

 blackish-brown mineral, found on the 

 Coromandel coast, and consisting of the 

 oxides of cerium, iron, manganese, and 

 titanium. 



TITANITE. Sphene. Silico-titanite 

 of lime, comprising the varieties of 

 brown and yellow menakan-ore, in large 

 crystals ; and that from St. Gothard 

 denominated rayonnante en gouttiere by 

 Saussure, on felspar with chlorite, &c. 



TITA'NIUM (T/ravo?, calx). A metal 

 which, in the form of titanic acid, con- 

 stitutes several minerals, as menachan- 

 ite, &c. 



TOADSTONE. A provincial term 

 applied to certain igneous or basaltic 

 rocks associated with the limestone 

 formation of Derbyshire. 



TO'DIDiE. The Todies; a family 

 of the Insessores, or Perching birds, in- 

 digenous in America, where they may be 

 regarded as representing the king-fishers 

 of the Old Continent. See Fissirostres. 



TOISE. Orgya. A French measure 



of length, consisting of six feet, or the 



ordinary height of man. It is employed in 



all the older French measures of the earth. 



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