Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/814

 ZOD

ZMILAMPIS, in natural hiftory, the name of a gem, de- fcribed by Pliny and the antients, which they tell us was very like the Proconnenfian marble, except that in the cen- ter of the ilone there was always a bluilh fpot, refembling the pupil of an eye.

The Proconneniian marble of the antients was of a fine clear and elegant white, variegated with irregular black veins. Pliny's defcription is lb ihort, that it has been fup- pofed from him that the Zmilampis was a fort of marble ; he only fays of it, that it was like the Proconnenlian marble, but blue in the middle. Many had inferred from this, that he meant no more by it than that this was a Hone, which had blue veins inftead of the black ones in the Proconnenfian kind. But when we examine the reft of the antients, and find that it was a fmall ftone, found in the river Euphrates, and worn in rings ; and that its blue fpot was like a pupil of an eye, we may eafily determine that it was one of thofe gems which we call oculus bcli, or bcllocchio ; of which there are a vaft variety found in the rivers of the Eait-indies, and many have a fine opake white ground, and a bluilh or green- ifh fpot for the pupil.

ZMILANTHES, in natural hiftory, a name given by Solinus, and fome others, to a gem called by the more correct wri- ters Zmilampis. Sec the article Zmilampis, fupra.

ZOCHINACAZTLIS, in botany, a name by which fome au- thors have called the jlos auricula, a flower of New Spain, ufed in the making of the Spanifh chocolate. Her- nand. p. 30. '

ZODIAC [Cycl) Zodiac of the comets. Caffini hath obfer- ved a certain traft in the heavens, within whofe bound (by many obfervations) he hath found moll: comets, tho' not all, to keep. This he makes as broad as the other Zodiac, and marks it with figns or constellations like that, which are, An- timiis, Pegafus, Andromeda, Taurus, Orion, the LeJJer Dog, Hydra, the Centaur, Scorpion, and Sagittarius.

ZODIACAL Light, a brightnefs refembling that of the milky way, and which is fometimes perceived in the heavens, at certain times of the year, after fun-fet, or before its rife. The form of this light refembles that of a pyramid, lying length ways in the Zodiac, within which its point and axis are always inclofed, its bafe being placed obliquely with refpe£t to the

- horizon. This phenomenon was Hrft difcovered, defciibed, and named by Mr. Caffini the elder. See Mairan, fuite des Mem. de 1' Acad Royale des Sciences, 1731. p. 3. The zodiacal light is nothing but the tolar atmofphere, a rare and fubtile fluid, either luminous by itfelf, or made fo by the lays of the fun furrounding its globe ; but in a greater quantity, and more extenftvely, about its equator, than any other. The zodiacal light is more or lefs viable according to circum- itances : But the folar atmofphere is not always vifible by means of this light, though it be always ken about the globe of the fun in total eclipfes.

One of the moll: eflential circumfrances for the perception of tbe folar atmofphere by the zodiacal light, is its having a fuf- ficisnt length on the Zodiac ; for, without this, its brightnefs is entirely hid from us by the twilights.

Mr. de Mairan fays^ it may be proved from many obfervations, that the fun's atmofphere fometimes reaches as far as the earth's orbit, and there meeting with our atmofphere, produces the appearance of an aurora borealis. See the article Aurora Borcalis, Cycl. and Suppl.

The length of the zodiacal light varies fometimes in reality, and fometimes in appearance only, from various caules. The oblique poli tion of this light, little different from that of the plane oS the ecliptic, does not permit us to fee itdiftincfly, and (ufficiently elevated above the horizon ; but fome time after iun-fct, towards the end cf the winter, and in fpring, or be- fore fun-rilmg in autumn, and towards the beginning of whi- ter. Several caulus hinder our feeing it, any more than the milky way ;. Inch as moon-light and llrong twilights, anions others. Mr. Caffini a often mentions the great refemblance of the zo-

- djacal light to the tails of comets. Mr. Fatio b has made the fame obfervation ; and Mr. Euler has lately endeavoured to prove them owing to fimilar caufes c. — [ a Decouverte de la lumiere celefte que paroit dans le Zodiaque, art. 41 . b Lettre a Mr. Caffini, printed at Amfterd. 1686. = Euler, in Mem. del* Acad, de Berlin, Tom. 2.] See the article Tails of Comets,

The figure of this folar atmofphere muft be lenticular, or that of a flatted fpheroid. Mr. de Mairan gives us a draught of its appearance and projection. Lib. cit. c. 4. fig. 1. The extent of the zodiacal light from the fun to its point, is feldom lefs than 50 or 60 degrees : It has even been known tcextend to 100 and 103. lb. c. 6. This light feems to have no other motion than that of the fur, itfelf. lb, c. 7.' Mr. Euler obferves, that if the fun has an atmofphere, the force of the impulfe of light ifluing from that globe, mult drive particles of that atmofphere before it ; but as gravity is very ftron* at the fun, this impulfe would never drive thofe

. particles beyond the limits of their atmofphere, were it not for the centrifugal force arifing from the fun's motion round its axis. This being oppofite to the a&ion of gravity, and dimi-

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nifhing its efFefls, the impulfe of the light may confiderably dilate the figure of the folar' atmofphere, from what it would be it it arole from the gravity and centrifugal force of its parti- cles only i and this dilatation will be very coniiderable near the fun's equator, and very fmall towards its poles. The action of light thus diminilhing the aaion of gravity, Mr. Eu- ler attempts to calculate how far this diminution of gravity may incrcale the extent of the fun's atmofphere about its equa- tor. He finds a cubic equation, the roots of which exprefs the feint-axis, or greateft amplitude of this atmofphere. He adds, that this equation having three real roots, it is poffible that the folar atmofphere may become a ring furrounding the fun's globe, as the ring of latum furrounds the body of that planet. Loc. cit. p. 140. ZONA, a word ufed by fome authors for that fpecies of herpes

which others call the zinzilla, and we term the Jliingles. ZGN1TES, inthe materia medica of the antients, a name given to a kind of tutty, called alio placitis. It had the latter name from the Greek, m„„ s, a crult, it being formed by way of crult on the fides of the furnaces. The latter name zonites was given it from its being formed of feveral coats, which, when broken tranlverfely, had the appearance of belts or zones, See the article i< urnace. ZONI IIS Cadmia, a name given by fome authors to a kind of cadmia tornacum, from its dually furrounding the upper parts ot the furnaces like a girdle or belt. ZOOLATR1A, Za^H,**, a fpecies of idolatry, wherein di- vine worlhip was offered to animals. Hcfm. Lex. in voc 1 he word is compofed of Zm, an animal, and l« K w ' or. fhip. ZOOLOGY, {Cycl.) the fcience of animals. This makes one ot the three kingdoms, as they are called, of natural hiftory ; the vegetable and the mineral being the two others : Its thefe' however, there is this difference made by writers, that while vegetables and minerals are treated of together, as all of a piece in each, the fubjeSs of Zoology are divided, and it is made to compofe, as it were, feveral kingdoms. Whoever is to write on plants and minerals, calls his woik a treatife of botany, or mineralogy ; and we have no words to exprefs any fubdivilion of them into kingdoms : but, in Zoology we treat, as different fubjeds, the different parts of it ; and the hiltory ot birds is feparated by fome from the reft under the name of ornithology ; that of quadrupeds under the name of tetrapodology ; and we have for the reft, the words entomo- logy, amplnhology, and the like, expreffing thefe things which are properly but the parts of Zoology, as fo many diftina and feparate ftudies.

Ibis may eafily be amended, by our confidering the animal world as we do the vegetable and mineral, and dividing it, as ■ we do the others, into its proper families; it will then be found that thefe are no better distinctions than thofe of the families ot thele things, and that the authors may as well fet up fepa- rate lludies under the names of bulbology, umbeUiferolon, and the like, as thofe.

A natural divifion of the fubjefls of Zoology, on this principle, will afford fix feveral families of its fulsje<fts. 1. The hairy quadrupeds. 2. The birds. 3. The amphibious animals, fuch as lerpents, lizards, frogs, and tortoifes. 4. The fifties. 5. The inlects. And iixthly, thofe loweft order of animated beiogs-the zoophytes. Jrtedi Ichthyol. See the articles Qua- druped, Bird, Fish, is'c. ZOOM1NERAL1A, a word ufed by fome writers to exprefs certain fubltances which are of animal origin, yet have fome- what of the nature of ftones, as pearls. ZOOPHTHALMUS, in botany, a name given by the antier.t Greeks to thijedum majus, or common great ho'ufe-leek. It had this name from the Greek Zoi,, an animal, and if S«f.- («;, an eye, as expreffing a refemblance to the eyes of large animals, in the round and radiated growth of its clufters of leaves. They alfo called it umbrofia. ZOOPHYTE {Cycl.)— Zoofhv.t E-Marygold. See the ar- ticle Marygold. ZOPHOCIDELUS, in botany, a word ufed fometimes as an epithet with the word chameleon, and fometimes fingly as the name of a plant, in both cafes expreffing the black chamaeleon- thiftle, which the antients carefully diftinguifhed, in their writings, from the white kind, the former being a poifonous plant, the other not fo. ZOPPO, in the Italian mufic, is applied to all thofe counter- points, defcribed under the articles Perfidiato, Obli- gato, cift. Thus -they fay eontra-punto alia zoppa, a lame or hopping counter-point ; becaufe, in thefe, a note is placed between two others, each of half its value in time : When this comes to be played or fung, the voice or inftrument feems to proceed by unequal leaps or fteps, like thofe of a lame ptt- lon. See the example here annexed.

There