Caufes and Reasons to omit cutting through this Ifthmus. THE firft fcruple was no doubt the greatness of the Work, for it would be no fmall Labour and Expence to cut thro' an Ifthmus, whofe Breadth at the narroweft Part is at least forty German Miles, and the Earth rocky; befides there must have been Dams and Wears made in several Places, which could not have been done without fkillful Workmen, which thofe Nations have always wanted. THE fecond Reafon was, because they fuppofed the Christian Nations in Italy, Venice, France, Spain, &c. would receive greater Benefit than they themselves from this Canal, by failing thro' it to Perfia and India, and bringing thence thofe precious Commodities, which the Turks and Egyptians at prefent carry at their own Prices by Land, and for which they receive large Duties, which bring confiderable Revenues into the Grand Seignior's Coffers. See Maffeus's Hiftory of India, Book iii. where he tells us, how much the Sultans of Egypt were formerly offended at the Portuguese failing and trading into India. A third Cause why they neglected this was perhaps, because they knew the Chriftians excelled them in Navigation; and were therefore afraid left they should invade thofe Streights, and the adjacent Countries, or even Medina itself, the Sepulchre of Mahomet. For a confiderable Fleet would in a short time transport a great Army of Men, and all neceffary Provifions from Europe to Arabia, by this Canal. BUT Alphonfus Albuquerce, Governor of the Portuguese Indies, was of another Opinion, when he had intended to have turned the Nile from Egypt, by cutting a Chanel thro' Abyffinia (which borders upon Egypt, only a few Defarts interpofing) to the Red-Sea, that by this means he might 0 2 render render Egypt barren and unfruitful to the Turks ; but he died before he could undertake it. THUS far, concerning the Altitude of the Mediterranean compared with that of the Red-Sea, Atlantic, and Indian Ocean. We were obliged to explain it because from thence fome take Occafion to argue the unequal Altitude of some Parts of the Ocean. BUT these things may be confirmed by another Example, if we may compare great Things with fmall. The German Ocean, which is a Part of the Atlantic, running between Friefland and Holland, forms a Bay; which tho' it be but fmall, in comparison of these famous ones juft now mentioned, yet it is called a Sea, and watereth Amfterdam the Capital of Holland. Not far from thence is the Lake of Harlem, which is alfo called the Sea of Harlem: this is as high as the forementioned Bay, and fends out a Branch to Leyden; where it is divided into feveral leffer Canals. And because neither the Lake nor the Bay overflows the bordering Country (when they are fettled and at quiet, and they have Bulwarks provided against a Storm) it appears that they are not higher than the Lands of Holland. But that the German Ocean is higher than these Countries, hath been experienced by the Inhabitants of Leyden, when they undertook to cut a Canal from their City to the German Shore, near the Town of Catwic, which is about two Holland Miles in Length; fo that the Sea being let in, they might fail into the German. Ocean, and from thence to other Countries. But when they had finished a great Part of it, they were forced to leave off, having at length found, by Obfervation, that the German Ocean was higher than the Ground between it and Leyden; from whence the Place where they left off is called by the Dutch, Het malle Gat. i. e. unprofperous. Therefore the German I German Ocean is fomething higher than [the Zuyder Zee or] the Bay of Holland. BUT all Bays are not depreffed below the Ocean, for those that run out into the Land at broad and open Paffages, fuch as thofe of Mexico, Bengal, &c. are, without doubt, of the fame Altitude with the Ocean itfelf: tho' I know the Spaniards doubted this (whether the Pacific Ocean was higher than the Bay of Mexico) when they confulted about cutting thro' the Ifthmus of Panama, that they might with more Expedition fail to Peru, China, and the Indian Inlands. But befides this Sufpenfe, we understand that they had a Political Reason for not doing it; they were afraid left the English, Dutch, and other Nations fhould make ufe of it, and lie in wait at the Entrances, or invade Peru. For the English and Dutch would not care to make fuch long and dangerous Voyages thro' the Streights of Magellan or La Maire, when, with a well furnished Fleet, they could force their way thro' thofe Streights, and perhaps take Peru, or at least crush the force of the Spaniards there. THAT we may put an end to this, it is best to determine, that the divers parts of the Ocean and broad Bays are all of the fame Altitude, (as was proved in the first Propofition) but long Bays, and chiefly those produced from narrow Streights, are fomewhat depreffed, efpecially at their extream Parts but I could wish there were more diligent and accurate Obfervations made by thofe who have the Opportunities of making them, to remove, if poffible, the following Doubts, viz. 1. Whether the Indian, Allantic, and Pacific Ocean are of the fame Altitude, or the Atlantic be lower than the other two. 2. Whether the northern Ocean, near the Pole, and within the Frigid Zone, be higher than the Atlantic, 3. Whether the Red-Sea be higher than the Mediterranean. 4. Whether the O 3 Pacific Pacific Sea be higher than the Mexican Bay. 5. Whether the Baltic be as high as the Atlantic. And these Differences ought to be observed in Hudson's Bay, the Streights of Magellan, and others. We fhall treat of the Euxine Sea in Chapter xv. THE continual Flux and Reflux of the Sea, and Currents, make the Face of the Ocean mutable, and it's Parts of a different Altitude, at different Times; but these arife from external Causes, and we here only confider the natural Conftitution of the Water: befides, they do not feem to alter the Altitude fo much in the middle of the Ocean, as near the Shores. COROLLARY. THEREFORE we cannot affent to Papyrius Fabianus and Cleomedes, who determined the greatest Height of the Ocean to be fifteen Furlongs, or half a German Mile; unless they mean the Depth, which is not at all well expreffed by the Word Altitude, as it appears in the Translation of Aristotle, Book i. Meteor. Chap. xi. at the end, where Babɛa T TOT is explained of the Altitude of the Sea. PROPOSITION VI. The Depth of the Sea, or Ocean, in most Parts may be tried with a founding Lead; and there are but few Places where the Bottom cannot be reached. THE Depth of the Ocean varies according to the greater or leffer Depreffion of the Chanels; being found of a German Mile, 20, 1, 4, 2, &c. deep; and in a few Places a whole German Mile or more, where the Line was commonly not long enough to try how much, tho' even there it is likely the Bottom is not at a vaft Distance, unless unless perhaps in fome Places there may be deeper Pits than ordinary, or fubterranecus Paffages. THE Depth of Bays is not fo great as that of the Ocean, and their Chanels are lefs hollowed by being nearer the Land: for the fame Reason the Ocean is not fo deep near the Shore, as in remote Places; which happens by reafon of the concave Shape of the Chanel. SAILORS find the Sea's Depth with a founding Lead, in the Shape of a Pyramid, of about twelve Pound Weight, faftened to a Line about two hundred Perches long, tho' fome require a Lead of a greater Weight: yet they may be fometimes deceived in this Obfervation if the Line fhould be carried away by a Current or Whirlpool, fo as not to defcend perpendicularly, but obliquely. BUT when the Depth is fo great that no Line is fufficient to found it, fome have thought of a Method to try it thus (d). In the first Place they obferve, how long a known Weight of Lead will be in defcending a known Depth; then they faften a Cork (d) The learned Dr Hook has given us a Method (much like the following) to found the Depth of the Sea without a Line, which, because it pro mileth Success, we fhall here defcribe from the Philof. Tranf. No 9. Page 147: Take a Globe of Fir, or Maple, or other light Wood, as A; (Fig. 19.) let it be well fecured by Varnish, Pitch, or otherwise, from imbibing Water; than take a Piece of Lead, or Stone, D, confiderably heavier than will fink the Globe: let there be a long wire Staple B in the Ball A, and a fpringing O 4 Wire C, with a bended End F, and into the faid Staple, prefs in, with your Fingers, the fpring ing Wire on the bended End: and on it hang the Weight D, by it's Hook E, and fo let the Globe and all fink gently into the Water, in the Pofture reprefented in the Figure, to the Bottom, where the Weight, D, touching firft, is thereby ftopped; but the Ball, being by the Impetus it acquired in defcending carried downwards a little after the Weight is ftop ped, fuffers the fpringing Wire to fly back, and thereby fets itself at Liberty to re-afcend And |