Pagina-afbeeldingen
PDF
ePub

THE Grecian Stadium, or Furlong, is fuppofed to be 600 of their Feet, which make 625 Roman, or Rhinland, Feet; their Foot being a little larger than the Roman.

A GERMAN Mile (15 of which Geogra phers allow to a Degree) contains 22800 Rhinland Feet, and is accounted 4000 Paces, or 32 Furlongs. It is in Proportion to the Rhinland Mile, as 19 to 15.

THE Italian or Roman Mile is 1000 Paces, which is equal to 4000 Rhinland Feet. Note, The Romans used to call their Mile Lapis, because a Stone was erected at the end of every Mile; efpecially in Places adjacent to the City.

AGEOMETRICAL Pace is exactly 5 Feet; and a Fathom 6 Feet; which is thought by fome to have been the Pace of the Grecians.

A CUBIT is fupposed to be a Foot and a half. THE Parafange, or Perfian Mile, is thought to be 30 Furlongs, or 3000 Perfian Paces.

THE Schanus, or Egyptian Mile, according to Herodotus, contains 50 Furlongs, tho' only 40 according to Pliny. Perhaps their Length differed in divers Places, or the Furlongs of the Authors might be unequal: Or very likely their Books are corrupted.

THE French League is in Proportion to the Rhinlandish Mile, as 19 to 25; and the Spanish League is to the fame Mile, as 19 to 27: But because in several Parts of France and Spain their League is found to differ, we cannot be well affured of the Length of these Measures.

THE English Mile is in Proportion to the Rhinlandifh, as 19 to 55, or as 19 to 60 (r). But there

(r) The leaft Part of English Measure is a Barley-Corn, taken out of the middle of the Ear

and well dryed; whereof 3 in
Length make an Inch, &c. as
in the following Table.
A Table

there are three forts of English Miles, whereof 27 of the longest, 50 of the middle Kind, and 60 of the fhorteft, make a Degree or 19 Dutch Miles.

THE Danish and Swedish Mile is to the Rhinlandish Mile as 19 to 10; tho' in fome Places they ufe the German Mile.

THE Voreft, or Ruffian, Mile is as 19 to 80.

THE Turkish League or Mile is faid to be equal to the Italian Mile; of which 60 make a Degree.

THE Arabian League was formerly accounted the twenty fifth Part of a Degree, or 19 Holland Miles: but they now use another of which 56 make a Degree.

A HUNDRED Indian Miles are thought to equal a Degree. Tho' the Indians commonly defcribe Distances by a Day, or an Hour's Journey.

THE Inhabitants of Cambaya and Guzarat, use a Measure which they call Coffa, of which 30 make a Degree.

THE Chinefe obferve three Measures in their Journies, which they call Li, Pu, and Uchan. Li is the Distance at which a Man's loud Voice may be heard on a Plain, in a calm Air; which is accounted 300 Geometrical Paces. Their Pu contains 10 Li's;

[merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

fo that 20 Pu's make a Degree. And 10 Pu's make an Uchan, or 30000 Paces; which they account a day's Journey.

Note, A Square Rhinland Mile confifts of Square Feet, and a Cubic Mile of Cubic Feet. Also a Mile multiplyed into itself makes a Square Mile; and that again by a Mile makes a Cubic Mile. The fame is to be understood of a Square and Cubic Foot.

SECT. II.

Containing fome general and abfolute Properties of the Earth, in five Chapters.

T

CHA P. III,

Of the Figure of the Earth.

HE first and noblest Property of the Earth (as exceeding the reft in being more useful and neceffary) is it's Figure; without the Knowledge of which there can be nothing well understood or demonstrated in this Science; and all the following Propofitions almost entirely depend on, or immediately flow, from this; which for that Reason ought to be first treated of.

THERE have been, and are to this Day, feveral Opinions about the Figure of the Earth; for the Vulgar that understand not Geography, imagine it to be extended into a vaft Plain bounded with a Circular Line; except where Mountains and Vallies interpofe. Of this ftrange Opinion was Lactantius and others of the Fathers, who ftrenuously argued that the Earth was extended infinitely down

wards,

wards, and established upon several Foundations (a). This they were inclined to think from fome Places of Scripture which they either ill understood or wrong interpreted. Heraclitus, that ancient Philofopher, is faid to have been of their Opinion: tho' others fay, he fuppofed the Earth to be in the Shape of a Skiff or Canoo, very much hollowed. But what is more strange Francis Patricius (a modern Philofopher of no fmall Repute in the laft Age) ftrenuously endeavoured to prove, that the Earth was horizontally stretched out and plain under Foot. Anaximander is faid by Peucerus to have fuppofed the Earth like a Cylinder; tho' that is not fo probable, because he tried to measure it, and also invented a fort of a Dial at Lacedæmon, upon which the Top of the Gnomon by it's Shadow marked out the Days of the Equinoxes, and Solstices: which fhewed him to have been tolerably skilled in Aftronomy, confidering the Time he lived in. Leucippus alfo thought the Earth to be in the Shape of a Drum. These with a great many other abfurd Opinions, are by Ariftotle and others attributed to the Antients: of which fee Ariftotle Lib. ii. Cap. 13. de Calo.

BUT the true and undoubted Opinion, which is defended by all Mathematicians, and almost all Philofophers, is, That the Earth is of a globular or spherical Figure (b).

(a) See Lactantius Lib. iii. Chap. 24. and Auguftin Lib. xvi. Chap. 9. De Civit. Dei. They thought their Opinion was favoured by the Pfalmift. Pfal. xxiv. 2. and cxxxvi. 6.

(6) Among the many excellent and wonderful Inventions of the modern Philofophers, this here is not certainly in the laft Place, nor hath the leaft

THE

Honour and Admiration in it; that the true Figure of the Earth, which Men have inhabited for fo many thousand Years, is but now begun to be known a few Years ago. For that which all Men thought to be globular and truly fpherical, is now found to imitate rather an oval Figure, or that of an Ellipfis revolved about it's leffer

Axis: So that thofe Diameters are longest which come nearest the Equator, and leffen as they become more remote, but the least Diameter of all is the Axis which joinech the two Poles. The Thing will perhaps be better understood if it be reprefented by a Figure.

Let apqp (Fig. 4) be a circular Section of the Earth made by the Meridian, such as it was thought to be formerly and pp the Axis or Diameter joining the Poles, and q the Diameter of the Equator: then the oval Line APQP, defcribed upon the Diameters EQ and PP, will represent the Section or true Meridian Line, which for Distinction fake is made here to differ more from a Circle than it really ought to do; but in truth, the Proportion is as 692 to 689. So that the Line CQ measuring the Altitude of the Earth at the Equator, exceeds CP the Altitude at the Pole 85200 Paris Feet, or about 17 Miles.

[ocr errors]

This Affair is well worthy to be traced to it's Original, and to be backed by a Demonftration, fo far as our Purpose will permit. See the Hiftory of the Royal Academy of Sciences by du Hamel. Pag. 110, 156, 206. Also Hift. de l Acad. Roy. 1700, 1701.

The French made an Experiment about forty Years ago, fhewing that a Pendulum (which is a well known Inftrument for measuring of Time) vibrates fo much the flower, by how much the nearer it is brought to the Equator: that is, the Gravity, or Celerity of Defcent of the Pendulum, and of all other Bo

dies, is lefs in Countries approaching the Equator than in Places near either Pole. The two famous Philofophers Newton and Huygens being excited by the Novelty of the Thing, and feacrhing more narrowly into the Caufe of it, found thereby that the Earth must have fome other Figure than what was known; and also demonftrated that this Diminution of Weight doth naturally arise from the Rotation of the Earth round it's Axis; which Rotation, according to the Laws of circular Motion, repels all heavy Bodies from the Axis of Motion: fo that this Motion being swifter under the Equator than in Parts more remote, the Weight of Bodies muft alfo be much less there than nearer the Poles. Therefore the Parts of the Ocean under the Equator being made lighter, and according to the Nature of all Fluids, preffed and forced on either fide by the Waters nearer the Poles, they must be raised up to a greater Height, that fo they may better fupport and balance the greater Weight of the contiguous Waters. Which mutual Libration is demonftrated upon Suppoftion of that Inequality of the Diameters which we mentioned above. The Figure of the Sea being resembled by the Lands adjacent, which are every where raised above the Sea, the aforefaid Form must be attributed to the whole terraqueous Globe. They that would be more fully informed in this Matter may confult Newton's Principia Lib. iii. Prop. 19. or Huygen's Trea tife of the Caufe of Gravity.

The

« VorigeDoorgaan »