TEM 



TEN 



means of which, the images are made to 

 appear in the same position as the ob- 

 jects. These are called double telescopes. 



TELESCO'PIUM. The Telescope; a 

 modern southern constellation, consist- 

 ing of nine stars. It is surrounded by 

 Ara, Pavo, Sagittarius, and Ophiuchus. 



TELLI'NlDiE. Solid and closed bi- 

 valves : a family of the macrotrachian 

 mollusca, in which the two siphons of 

 the animal are of enormous length. 



TELLINI'NiE. A sub-family of the 

 Tellinidce, named from the genus tel- 

 lina, in which the siphons are exces- 

 sively long. 



TE'LLOGRAPH (xfiXe, afar off, \6yoi, 

 a word, 'fpd<p(a, to write). This term, 

 contracted from telelograph, is used by 

 Edgeworth, who observes that while 

 " telegraph is a proper name for a ma- 

 chine which describes at a distance, tele- 

 lograph, or, contractedly, iellograph, is a 

 proper name for a machine which de- 

 scribes words at a distance." 



TELLU'RIUM {tellus, the earth). A 

 rare metal of a brilliant silvery-white 

 lustre, found in abundance at Schemnitz, 

 in Hungary, combined with bismuth; 

 and in the silver mine of Sadovinski in 

 the Altai, united with silver and with 

 lead. With oxygen, it yields the tel- 

 lurous and the telluric acids. 



Telluretted hydrogen. A gaseous com- 

 pound of tellurium and hydrogen, ana- 

 logous in constitution and properties to 

 sulphuretted hydrogen. 



TEMPERAMENT {tempero, to mix 

 together, to temper). Crasis. A mixture 

 or tempering of elements ; a notion 

 founded on an ancient doctrine of four 

 qualities, supposed to temper each other : 

 these are, in the abstract, hot, cold, dry, 

 moist ; in the concrete, fire, air, earth, 

 water. 



TEMPERAMENT, EVEN. A musi- 

 cal instrument is said to have an even 

 temperament, when it has been so tuned 

 that the differences between the inter- 

 vals are perfectly equalized. To accom- 

 plish this, the difference, must be so dis- 

 tributed among all the semitones of the 

 octave, th^t, when sounded, they do not 

 bear an exact ratio to any fundamental 

 note whatever, but the deviation is so 

 small as to be imperceptible. 



TEMPERATE ZONES. The two di- 

 visions, or belts, of the surface of the 

 earth, which lie between the Tropics and 

 the Polar Circles— one in each hemi- 

 sphere. They are named from their tem- 

 perature being free from the excessive 

 331 



heat of the Torrid, and from the exces- 

 sive cold of the Frigid Zones. 



TE'MPERATURE {tempera, to mix 

 various things in due proportions). The 

 comparative degree of active heat accu- 

 mulated in a body, as measured by an 

 instrument, or by its effects on other 

 bodies. By the term mean annual tempe- 

 rature is meant the temperature obtained 

 by adding together the temperatures of 

 all the months of the year, and dividing 

 the sum by the number of the months ; 

 so that the mean annual temperature ex- 

 presses that height at which the thermo- 

 meter would stand at any place, if we 

 could suppose it perfectly stationary 

 throughout the whole year. 



TEMPERING. The operation of heat- 

 ing iron to a certain extent, indicated by 

 the colour presented on the surface of 

 the metal. 



TEMPORARY STARS. Stars which 

 have appeared, from time to time, in 

 different parts of the heavens, blazing 

 forth with extraordinary lustre, and, after 

 remaining awhile apparently immove- 

 able, have disappeared and left no trace. 

 Of this kind was the star which appeared, 

 A.D. 389, near a Aquilas, and, after re- 

 maining for three weeks as bright as 

 Venus, disappeared entirely. 



TENA'CITY {tenax, capable of hold- 

 ing). The degree of force with which 

 the particles of bodies cohere, or are held 

 together ; a term particularly applied to 

 metals which may be drawn into wire, as 

 gold and silver. 



TENDENCY. This word is employed 

 in two senses. By a * tendency ' towards 

 a certain result is sometimes meant, * the 

 existence of a cause which, if operating 

 unimpeded, would produce that result.' 

 In other cases, a ' tendency' towards a 

 certain result is understood to mean ' the 

 existence of such a state of things that 

 that result may be expected to take place.' 

 In the former sense, we say that the 

 earth has a tendency to fly off at a tan- 

 gent ; but in the latter, the earth has a 

 greater tendency to remain in its orbit 

 than to fly off from it. In the former 

 sense, it may be said that population has 

 a tendency to increase beyond subsist- 

 ence ; in the latter, that subsistence has a 

 tendency to increase at a greater ratio 

 than population. Whately. 



TENDRIL. Cirrhus. A particular 

 form of the petiole in certain plants, as 

 the vine; it appears to be a contrivance 

 employed by nature to support plants by 

 the aid of others, and was included by 



