THR
yarn of (lieeps wool, which they weave into garters and a fort of ribbands, ufed by way of ornament ; but they place . no value on it, becaufe of us want of ftrenethJ Schefer's Hill. Lapland. ° M
Air-1 hheads, a term ufed by fome to exprefs thofe fine long white filaments or thready fubitances, which we meet with in Vaft numbers floating about in the air, in-Auguft and September. i he world has been much perplexed about the generation of thefe, till it was known that they were the work of fpiders, and that they ferved thefe creatures to move from place to place by. 'I hey are long, downy, and very foft, and though they hold together when untouched, they ftick to the fingers iii handling, and eafily break with a flight touch. I he greater number of fpiders have the property of (pinning this fort of Thread. The long-legged rield-fpider, called the Jhepberd, and fome others, want it ; thefe have nothing to do with the Air-threads, fo much wondered at j but all the o- thers, that is, all thofe which nature has endowed with a power of fpinning, make them.
The general method of thefe creatures fpinning and weaving their webs, is by letting down the thread and then drawing it after them, and fo dilpofing it as they think proper ; but in the midit of their work of this fort, if they are clofely ob- ierved, they will be fometimes found to dcfiit, and turning the tail to the contrary way of the wind they will emit a thread with great violence, no ltfs than that with which a jet of wa- ter is difcharged from a cock. In this manner they continue darting forth the thread, which the wind takes, and carrying it forward it foon becomes many yards long. Soon after this the creature will throw herfelf oft from the web, and trufting herfetf to the air with this long tail, will afcend fwiftly, and to a great height with it. The fragments of thefe lines, or the whole lines, and the fpiders attached to them though un- obferved, make thefe Air-threads, and the ufe nature deflines them for, is evidently the wafting the creature along the air, and giving it an opportunity of preying on gnats, and many other infects that inhabit the air, out of the reach of theie creatures by any other means.
'I he young fpiders, as well as the old ones, have this proper- ty of fpinning Threads, and failing in the air by means of them j and it is common to fee very minute fpiders at the ends of very long lines. No one particular kind is famous more than the reft for this practice, but all that can (pin, ai the proper feafon of the year do it.
The threads themfelves fhew the ufe they are of to the crea- ture in feizing its prey - y for they, as well as the webs below, are ufually found filled with the fragments of devoured ani- mals, the legs of flies, and the like.
When the Threads are newly fpun, they are always fingle, and are generally fcen afcending up higher and higher in the air i but when they are feen coming down, they are found fometimes compofed of three or four others, and either with- out any fpider at the ends, or with two or three or more. It is plain that this happens from the meeting of thefe threads one with another in the air, and their tangling together ; and this incommodes the creatures, and brings them down. The whole procefs of the workmanfhip of thefe threads is eafily feen, by obferving fume of the fpiders which have not yet mounted Into the air, but feem to be meditating their flight. It is common to fee one of thefe creatures at fuch a time mount the top-mod branch of a bufh, and from thence dart out at its tail one after another feveral of thefe long Threads, by way of allaying what it can do, and how it {hall like them. When the creature has darted out a thread to the length of feveral yards, it will of a Hidden draw it all up again, and wind it up into a fink- with its fore-feet ; but more frequently they break it off, and let it go. One fpider will fometimes dart out, and break off in this manner a great number of Threads, before it fpins one that it will trult to ; but at length it will pleafe itfelf with fome one, and commit itlelf to the air on it.
Thefe broken Threads are what fill the air with the loofc threads we fee in autumn ; and as thefe foon entangle to- gether, and bring one another down, it is no wonder that they are more frequent in the lower regions of the air, than thofe with the fpiders adhering to them, which ufually rife to great heights, and fuftain themfelves there. And hence the origin of the Threads was much perplexed among the en- quirers, becaufe they were found without any mark of the ani- mal to which they owed .their exiftence. The bufinefs of feeding is not all the ufe of thefe Threads, but the creatures evidently fport and entertain themfelves by means of them, floating about in the air, and changing height and place at pleafure.
When a fpider has once raifed itfelf from the earth in this manner, it does notdefcend always on the fame Thread \i a- rofe by, but draws that up at times, and winds it up into a hank with its fore-feet, and darts out another by way of fup- port ; and the new Thread is made more or lefs long, as it is intended for a higher or lower flight,
1 hefe Air-threads are not only found in autumn, but even in the depth of winter. The fercne days about Cbriftmas bring out great numbers of them ; but thc'Threads are at this feafon only fhort and {lender. They are the produce of the young Suppl. Vol. il.
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fpiders, hatched only the autumn before, and are fildom ufed to fuftain the animal, hut feem a mere fporting of it, being thrown out and broke off at (mall lengths. The thicker ropes of the autumn are the only ones intended for the fupport of the old fpiders in the air, when there is plenty of (mail flies that inhabit the airy region, and make it worth the creature's while fo take up its habitation among them. Phil. Tranf N°. 50.
I HRLX, among the Romans, an appellation given to gladi- ators, either becaufe they were natives of Thrace, or wore
ttjij 1 ™' r tlle manner °f tnat country. Pitijc. in voc.
THRIFT, Siaiice, in botany. See the the article Sta- tice.
I he feveral more common fpecies of this plant have been uled to be raifed promifcuoufly for making the edges of flower- beds, inflead of box; but the ncceffity of tranfplanting them every year to keep them within due bounds, has made them of late much difuled.
J hey are all propagated by parting their roots ; the beft time for doing which is in autumn, and they will grow with very little trouble, and flower in the May following, continuing i„ flower about three weeks or a month, if the weather is not too dry. Miller's Gardener's 0ia.
THRIO, ; «, in antiquity, a feflival in honour of Apollo. Palter, T. I. p. 405.
THRIPS, in natural hillory, a name ufed among the antients, to exprefs a fort of worm hatched from the egg of a beetle; which, while in the worm-flate, eats its way into wood, and forms cells and cavities in it of various fhapes, and in various directions, often refembling the figures of letters or other things.
The antient Greeks are faid to have ufed fmall pieces of the wood thus eroded in particular forms, as fcals before the en- graving of thefe utenfils was invented, and indeed they muff, very well have ferved this purpofe, flnce it is fcarce pofiible to conceive how one of thefe pieces of corroded wood ihould be counterfeited, or the impreffion imitated. Lucian mentions his marking his olives with a fignature of one of thefe pieces of wood greatly eroded, and ufes the word Thrips, not as the name of the animal, but of the piece of wood eroded by it. Theophraftus, Pliny and Ariftotle, alfo ufe the fame expreffion ; and we find that the word Thrips was as frequently ufed to fignify the pieces of wood, eroded, as the animal which eroded them.
THRISSA, in ichthyology, the name given by the Greeks and by the modern Latin writers, to the fifh which we call the Jhad, or the mother of the herrings.
This is called by Artedi the clupea, with the top of the up- per jaw divided, and with black fpots on each fide. This accurate author obferves alfo, that the agomts or agonc of Sal- vian, the farachus of Charleton, and the alofa minor and ha- rengus minor of Willughby, and others, which we call the pilchard, differ only from the Thrijftt in fize ; all bein<r the va- rieties of the fame fpecies of fifh, and all charactered by this fpecific name.
THROAT [Cycl.) — oW-Throat, in medicine. See the ar- ticle Quinzy, Cycl. and Suppl.
Throat-Fib, in botany, the name of a plant of the bell- flower kind, called in Latin Trachelitis!. Its characters and fpecies, fee under that head.
'This plant yields, when wounded, a milky juice in great plenty, and this if received into a Ihell or other fmall veflel, curdles immediately, and the whey runs from the thick part ; this whey is of a brown colour, whereas that of the wild let- tuce is of a fine purple, and dries into a cake that may be crumbled into a purple powder. The juice pf the Throat- wort fmells four, and its curdled part being dried burns like refin at the flame of a candle. Phil. Tranf. N°. 224.
THROMBUS, a word ufed by fome medical writers, to ex- prefs a grume or clot of blood.
THROSTLE, an Englifh name for the common mavis, or fong-thrufh. SeeTuRDUS.
THROWING, among bowlers. See the article Bowl- ing.
THRYALLIS, in botany, a name given by Nicandcr, and fome other writers, to a fpecies of mullein ufed in the coronas and garlands of the antients ; and, as he exprefsly fays, diffe- rent from the common wild mullein.
Diofcorides feems to make this his third fpecies, and calls ft lyehnitis, from its ufe in lamps ; the Greeks beating out its thready ffalks, and ufing them for the wicks of lamps. We have a kind of verbafcum, or mullein, which we call lychnitis, in commemoration of Diofcorides's name ; but it does not appear to be the fame fpecies that Nicander and the other Greeks called by that name. Some alfo called it ne~ keia, or necuia, from its ufe in making a kind of torch ; that was the thing with which they kindled the funeral piles of the dead.
THUMB, Pollex, in anatomy, one of the members, or parts of the hand. See the article Hand, Cycl. and Suppl 'The firfl: phalanx of the bones of the Thumb is not like thofe of the other fingers. Antient authors reckon it among the bones of the metacarpus, which it refembles very much, and by this means allow only two phalanges to the Thumb, and L 1 1 1 make
