Page:Cyclopaedia, Chambers - Volume 2.djvu/703

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Trunk cannot produce them, as being it felf no more than a Packet of Fibres, deftitute of all Aftion: Korean the Sap, which, like the Blood, is fit to nourifh the Parts, but not to form any new ones. The Branches there, of exifted before the Tree was lopped, and if they had appeared, would have bore an equal Number of Grains as thofe which did. Theft Grains, therefore, they mutt already contain in little. On this Footing, the Tree may be faid actually to contain in itfelf 15840000000 Seeds', wherewith to multiply itfelf as many times : But what fhall we lay, if each Seed, or Grain of a Tree, contain in itfelf another Tree, containing the fame Num- ber of Seeds ? And, if we can never come either at a Seed which does not contain Trees, nor at a Tree which does not contain Seed? By this Means we fhall have, an increafing Geometrical Progrcffion, the firft Term whereof is 1. the fecond 15840000000,- the third, the Square of 15840000000 y the fourth, its Cube, l$c. to Infinity. ' . -.

Several Species of Plants have been always iuppofed to be deftitute of Seed, in regard, no Obfervation, no Microfcope, no Anatomy, difcovered any Thing like them : Such are the Capillaries, the fiveral Kinds of Fuci, Sea- plants, Moffes, i£c. But the happy Induftry of the pre- ft-nt Age has difcover'd the Seeds of fome of them ; and

' has left us out of all Doubt, that the reft are not without the lame. The Seeds of Fern, and the Capillary-Plants, were firft difcovered by Cefms 5 and fince, more fully and critically by M. IV. Cole. The Seeds of fome Sea-Plants, were difcover'd by the Count de Marfigli, and thofe of others, by M. Reaumur, the firft mentioned in the Hi- ftory of the French Academy, for the Year 1712, and the latter for the Year 171 1. The Seeds of fome Kind of Fuci have been difcovered by Mr. Samuel lioody 5 thole of Coralloid Shrubs, by Dr. 'fane. Robin/on, as alio, thofe of feveral Fungi, particularly Truffles, and Crepitus Lupi's, or Puff balls 3 and thofe of fome other by Dr. Lifter. See Mushroom. Under which Article, a new Theory of a 'Propagation ofthefe apparently Seedlefs 'Plants is laid down.

Seeds, in Gardening, and Agriculture. Mr. "Bradley oblcrves, That the Seeds of Plants, though exceedingly good, will degenerate from the Mother-Plant, if they be ibwn on the fame Ground, whence they were gathered ; fo that thete is a great Neceflity for a yearly Change for Seeds of Foreft Trees, as Acorns, Maft, iSe. If the Place be too cold to fbw them when gathered in Auguft, they may be kept barrelled or potted up, in moift Sand or Earth, Jtratum fufer ftratum, during the Winter, at the End of which they are found fprouted, and if gently fown, will be as forward as if fown in Autumn, befides their miffing the Vermine to which the Winter Seed is much expofed. The Seed not to be chofen from the moll fruitful Trees, fo much as from the mod folid and fair 3 nor covet the largeft Acorns, but the moft weighty, clean, and bright. Porous, infipid, mild Sorts of Seeds, to be fown as loon as ripe. Hot, bitter Seeds _ to. be kept a Year before (own. The Shape and Weight of

' Seeds, direct how they are to be fet. Moft of them, when they fall, lie on one Side, with the fmall End to- wards the Earth, which fhews that Poflure to be beff to fet any Stone or Nut in : If they be heavy, fbw them the deeper. Acorns, Peaches, !jc. to be fown 2 or 3 Inches deep. See Seminary and Semination.

Seeds, in Pharmacy, (5'c. The Seeds ufed in Medi- cine, tic efpecially thofe imported from the Indies, Le- vant, (Sic. are federally defcribed under their refpeflive Articles, which fee. Among thofe cultivated at Home, the Principal are the Four hot, and rhe Four cold Seeds, as they are called. The firft are thofe of Annis, Fennel, Cummin, and Caraway ; the latter, thofe of Gourd, Pump- kin, Melon, and Cucumber. The Ufe of the four cold Seeds is for the making of Emulfions, cool, refrefhing Drinks, Palis for the Hands, and Oils ufed by the Ladies for the Completion.

Seed of Pearls, - ? g £(, £ Pearl. Semen Sanftum, or Santonieum, 5 i Wormseed.

SEEDLINGS, ate fuch Roots of Gilliftowers, as come from Seed fown 3 alio the young tender Shoots of any Plants, that are newly fowed.

SEEING, the Act of perceiving Objects by the Organ of Sight 5 or the Senfe we have of external Objects, by means of the Eye. See Sight.

For the Apparatus, or Difpofaion of the 'Parti neceffary to Seeing ; See Eve.

For the Manner wherein Seeing is performed, and the Laws thereof; See Vision.

Our beft Anatomifts differ greatly as to the Caufe why we don't fee double with the Eyes. Galen, and others after him, alcribe it to a Coalition or Decuflation of the

Optic Nerve behind the Os Sphencidcs. But whether they decuffate or coalelce, or only barely touch one another, is not 16 well agreed. The Barthclmcs and Vejaliu^ fay exprefly, they are united by a perfect Confufiou of their Subftance : Dr. Gibfou allows them to be united by the clofeft Conjunction, but not Confufion of their Fibres. 'Des Carles and others, account for the Effect another v^,. v,z. by fiippoftng that the FibrillrS conftiruting the rne- dullary Part of thofe Nerves, being Ipread in the Retina of each Eye, have each of them correlpor.ding Parts in the Brain 3 fo that when any of thofe FlbrilQ are ftruck by any Part of an Image, the corteipondmg Parts of the Brain are affected thereby. Somewhat like which is the Opinion of Dr. Briggs 5 who takes the Optic Nerves of each Eve to confift of homologous Fibres, having their Rife in the Thalamus nervorum Opticorum, and thence continued to both the Retime which are competed of them : And far- ther, that thofe Fibrillce have the fame Parallelifm,Tenfion, Sfjc. on both Eyes: Coniequenrly, when an Image is painted on the fame correfpomling, fymparhizing Parts of each Retina, the fame Effects are produced, rhe fame Notice carried to the Thalamus, and fo imparted to the Soul. Hence that double Vifion enfuing upon an In- terruption of the Parallelifin of the Eyes, as when one Eye is deprefTed by the Finger, or their Symphony in- terrupted by Difcafe. But pr. Briggs maintains* that 'tis but in few Subjects, there is any Decuffation 3 in none, any Conjunction more than mere Contact.

Whence it is that we lee Objects erect, when, as tia certain, the Images thereof are painted invertedly on the Retina, is another Difficulty in the Theory of Seeing. 'Dei Cartes accounts for i t hence 3 That the Notice the Soul takes of the Object, does not depend on any Image, nor of any Action coming from the Object, but merely from the Situation of the minute Parts of the Brain 5 whence the Nerves arife. Fgr. the Situation of a Capillamcnt of the Optic Nerve, correfponds to a certain Patt of the Brain 3 which occafions the Soul to fee all thofe Places lying in a right Line thetewith. But Mr. Aiclyneux gives us another Account : The Eye, he obferves, is only the Organ, or Inftrument : 'Tis the Soul that fires. To en- quire, then, how the Soul perceives rhe Object erect by an inverted Image, is to enquire into the Soul's Faculties. Again, imagine that the Eye receives an Impulfeon its lower Part, by a Ray from the upper Part of an Object 3 muff not the vifive Faculty be hereby directed to confider this Stroke as coming from the Top rather than the Bottom of the Object, and confequently, be determined to conclude it the Reprefentation of the Top ?

SEELING. A Horfe is faid to Seel, when upon his Eye-brows, there grows about the Breadth of a Farthing of white Hairs, mixed with thofe of his natural Colour; which is a Mark of Old Age : An Horfe never Seels till he is Fourteen Years old, and always before he is Sixteen at fattheft: The light Sorrel and Black, iooner Seel than any other. Horfe- Jockeys ufually pull out thofe Hairs with Pincers 3 but if there be to many, that it cannot be done, without making the Horfe look bald and ugly, then they colour their Eyebrows, that they may not appear old.

SEGMENT of a Circle, in Geometry, a Part of a Circle comprehended between an Arch and the Chord there- of. Thus the Portion AFB A (Tab. Geometry Fig. 13) comprehended between the Arch AFB, and the Chord A B, is a Segment of the Circle ABED, fgc. a Segment of fo many Degrees. The Term Segment is alfo applied by Extenfion, to Ellipfes and other Curvilinear Figures. As 'tis evident every Segment of a Circle muft either be greater or lefs than a Semi-circle 3 the greater Part of the Circle cut off by a Chord, i. e. the Part greater than a Semi-circle, is call'd rhe greater Segment, as ADEBj and the leffer part, the Part lefs than a Semi-cirde, the lefjer Segment, as A F B, £s?c. The Angle which the Chord A B, makes with a Tangent L B, is called the Angle of a Segment. Some, indeed, call the Two mixt Angles comprehended between the Two Extremes of the Chord, made with the Arch, Angles of the Segment.

The Height of a Segment F a, and half its Bafe er Chord B a, being given, to find the Area of the Segment: Find the Diameter of the Circle. (See Diameter ) (Jn this defcribe a Circle, and draw the Bale of the Segment AaB; draw R, AC, BC; and find the Number of Degrees of the Arch A F B. from the Diameter had, and its Ratio to the Periphery, find the Periphery idelf 3 and from the Ratio of the Periphery to the Arch ADB, and the Periphery itfelf, find the Length of the Arch ADB. This done, find the Area of the Scftor A FBCA. See Sector. And that of the Triangle A B. S e ? Triangle. Laftly, fubtraft the Triafigle from the Sector, the Remainder is the Area of the Segment.

If the Area of rhe greatM Segment ADE B were re- quired, the Triangle ACB muft be added to the Seaor

A DE