T E M
T H A
T.
TADORNA, the name of a fpecies of duck, printed tadoma in the Supplement, by an error of the prefs. See the article Tadoma, Suppl. TANNER, a perfon who drefTes hides by tanning. See the article Tanning, Cycl. and Suppl.
TANSEY, or Tanzy, the Englifh name of a genus of plants. See the article Tanacetum, Suppl.
/^Tansey, a name bywhich fome call the potentilla. See the article Potentilla, Suppl.
TARE, wV/V, in botany, the name of a genus of plants, other- wife called vetch. See the article Vicia, Suppl.
TARRAGON, a name fometimes given to abrotanum, or fouthernwood. See the article Southernwood, Suppl.
TEA, thea, in botany, is made a diftinct genus of plants. See the article Thea, Append.
TEDDER, or Tether, a rope tied to a horfe's foot, that he may grafe within a certain compafs. Ruft. Diet, in voc.
TEG (Suppl.) — Teg, among fportfmen, denotes a doe of the fecond year. Ruft. Diet, in voc.
TELAUGIA, in natural hiftory, the name of a genus of fcrupi, of a glittering appearance, ufually containing flakes of talc, and emulating the flrudture of the granites. Hill, Hift. Foil", p. 547, See Scrupi, Append. Of this genus we have the following fpecies. 1. The hard, fliining, black and white telauglum. 2. The hard, fhining, red and white telaugium. 3. The red telaugium, variegated with white and black. 4. The hard, heavy telaugium-, of a greyifti black, variegated with white. 5. The brownifh red telaugxum, variegated with white and yellowifh. 6. The reddifh white telaugium, variegated with black and gold co- lour. 7. The hard, white ielaugium, variegated with brown. " 8. The blutfh white, brittle telaugium. 9. The brown, fri- able telaugium, variegated with yellow. 10. The hard, pur- plifh brown telaugium, variegated with white and yellow. Ii. The heavy, red telaugium, Variegated with black and . white. 12. The hard, bluifh green tclaugium y variegated with white. Id. ibid. p. 547— -556.
TELEPHIASTRUM, bajlard orpine, in botany, the name of a genus of plants, 'called by Linnaeus anacampferos. See the article Anacampseros, Suppl.
TELESCOPE (Cycl.)— Mr. James Gregory was undoubtedly the firft inventor of reflecting tele/copes. The construction of his tele/cope is different from that of Sir Ifaac Newton, and in fome refpects not fo advantageous, as is fliewn in Phil. Tranf. N" S3.
Mr. Gregory defcribes this tele/cope at the end of his Optica Promota, published in 1663 ; being led into the invention of it, not by the confederation of the different refrangibility of the rays of light, which was not then known, but by an inconvenience he forefaw would follow from an hyper- bolic object-glafs. For he obferves, that if it be fufficiently " : ' broad to receive light enough into a teltfeope that mail magnify very much, it muft ©f confequence be very thick ; in which cafe, the.cleareft glafs would hinder too much of the light from being tranfmitted. He might alfo have add- ed another inconvenience, that though it will collect a pen- cil of rays coming parallel to its axis into a fingle point, yet it cannot collect the rays of an oblique pencil fo accu- rately as a glafs confuting of fpherical furfaces will do, as ■has been found by experience ; and therefore fpherical lenfes, upon this and fome other accounts, are fitter for optical ufes than thofe of any other figure.
Thefe reflecting tele/copes were not brought into practice till 1 7 19, by Mr. John Hadley; Sir Ifaac Newton's firft, and that of Mr. Gregory foon after. This laft, in fmall lengths, has an excellent effect, and is exceeding commo- dious. We-have a defcription of it by Dr. Smith % which differs from that of its inventor chiefly in this, that he di- rects his larger reflecting concave lens to be made of a pa- ■ rabolic figure, and his leffer of an elliptical one, inftead of the fpherical ones now ufed, as being the only figures that can be polifbed without infuperablc difficulties.— [* Optics, in the remarks, feet. 137, feq.j
Reflecting telefcopes have been greatly improved by Mr. Short; but the particulars of his method are not publifhed. ' For the theory of thefe and other telefcopes, fee Dr. Smith's Optics.
Telescope-^//, the Englifh name of a fpecies of turbo, of a conic figure, with- plane, ftriated, and very numerous fpires. See the article Turbo, Suppl.
TEMPERAMENT (Suppl.)— As Huygens has not given the
names of all the intervals that occur in his temperate fcale,
we fhall here infert them in the octave, from C to c, with
their refpective meafures in commas, and tenths of a comma.
Append, Vol. II. 1
Intervals. FromCtoD bb .
o#;
Db.
c#f.
E bb ,
Df. E».
Names.
Meafures.
E.
¥\
E#.
F.
&*.
F#.
G».
F##.
G.
A' b .
Gf.
a":
G#f
A.
B b >.
• 9-
A*.
25 26.
A## B.
27 28
B#.
29. 30
c.
3 1
Diminiflied fecond, extreme flat
fecond, or enharmonic diefis, Semitone minor, or chromatic
diefis, Flat fecond, or femitone major, Double femitone minor, Second, or tone, Diminiflied third, or extreme
flat third, Superfluous fecond, Third minor, or flat third, Extreme fuperfluous fecond, Third major, or fharp third, Diminiflied fourth, Superfluous third, Fourth,
Extreme diminiflied fifth, Falfe fourth, or tritonus, Falfe fifth, or femidiapente, Extreme fuperfluous fourth, Fifth, Diminiflied fixth, or extreme
flat fixth, Superfluous fifth, Flat fixth, or fixth minor, Extreme fuperfluous fifth, Sharp fixth, or fixth major, Diminiflied feventh, or extreme
flat feventh, Superfluous fixth, Flat feventh, or feventh minor, Extreme fuperfluous fixth, Sharp feventh, or feventh major, Diminiflied octave, Superfluous feventh, Oflave,
1.8.
3.6.
5-4- 7.2. 9.0.
1 o.g. 12.6. 14.4. 16.2. 18.0. 19.8. 21.6.
23-4- 25.2.
30.6. 324.
34-2.
36.0. 37.8. 39.6. 41.4.
43-2-
45.0. 46.8. 48.6. 50.4. 52.2. 54.0. 55.8.
The temperate diefis enharmonica of Huygens being 1.8 com- ma, nearly, which is eafily remembred, the meafure of any interval in the octave may be found by multiplying it by the number denoting the place of that interval. Thus the fixth minor, being the twenty-firft interval, will be — 1.8 x 21 = 37.8. The octave being the thirty-firft, will bez=3i X 1.8 £s 55-8, which does not differ from the truth by more than 0.00237, ^ at ' s > not ty -jTTj-s °f a comma, and there- fore perfectly infenfible. See Interval, Suppl. All the intervals in the foregoing table, either have .re- ceived names, or at leaft might receive them, from a per- fect analogy to the names in ufe among practical muficians ; but many of thefe intervals are as yet unheard of among practitioners. Perhaps, if all the genera of antient mufic were reftored, every interval here mentioned might be of ufe, either in melody or harmony, and -thereby greatly add to the variety of compofition.
TENDERLINGS, a name given to the foft tops of deer's horns, when they begin to fhpot forth. Ruft. Diet, in voc.
TENDREL, a term peculiarly applied to the young flioot, or fprig of a vine.
TENEBRIO, the Jlinking beetle, the name of a genus of beetles, the antennse of which are oblong, flender, and fi- liform.
It has no interior wings, in which Angular deficiency it dif- fers widely from all other beetles ; but the form and ftr-iic- ture of all its other parts refer it to this clafs. Sec the article ScaraBjEus, Suppl.
Mouffet has called it the Malta fceiidai There are feveml fpecies of it.
TERRA alana, a name fometimes given to the yellowifh white tripol'i. See the article Tripoli, Cycl. and Sup~ plement.
TETHYS, in zoology, the name of a genus of naked fea- infects, the bodies of which are formed, as it were, of two lips, with an oblong cartilaginous body between them. They have four tentacula, fhaped like ears, and there are two perforations in moft fpecies near the tentacula. ; - There are feveral fpecies of this genus... Vid. Hill, Hift. Anim. p. 92.
THATCH, a common covering for hgufes in moft parts of the country.
The belt kind of thatch is that called helm, or ftiff unbruifed wheat-ftraw, with the ears cut off, and bound up in bun- dles. This being difpofed in an uniform and longitudinal D d ©rder
