A Short Account of the Cause of the Saltness of the Ocean, and of the Several Lakes That Emit no Rivers; With a Proposal, by Help Thereof, to Discover the Age of the World. Produced before the Royal-Society by Edmund Halley, R. S. Secr.

V. A short Account of the Cause of the Saltnefs of the Ocean, and of the several Lakes that emit no Rivers; with a Proposal, by help thereof, to discover the Age of the World. Produced before the Royal-Society by Edmund Halley, R. S. Secr. There have been many Attempts made and Proposals offered, to ascertain from the Appearances of Nature, what may have been the Antiquity of this Globe of Earth; on which, by the Evidence of Sacred Writ, Mankind has dwelt about 6000 Years; or according to the Septuagint above 7000. But whereas we are there told that the Formation of Man was the last Act of the Creator, 'tis nowhere revealed in Scripture how long the Earth had existed before this last Creation, nor how long those five Days that preceded it may be to be accounted; since we are elsewhere told, that in respect of the Almighty a thousand Years is as one Day, being equally no part of Eternity; Nor can it well be conceived how those Days should be to be understood of natural Days, since they are mentioned as Measures of Time before the Creation of the Sun, which was not till the Fourth Day. And 'tis certain Adam found the Earth, at his first Production, fully replenished with all sorts of other Animals. This Enquiry seeming to me well to deserve Consideration, and worthy the Thoughts of the Royal Society, I shall take leave to propose an Expedient for determining the Age of the World by a Medium, as I take it, wholly new, and which in my Opinion seems to promise success, though the Event cannot be judged of till after a long Period of Time; submitting the same to their better Judgment. ment. What suggested this Notion was an Observation I had made, that all the Lakes in the World, properly so called, are found to be Salt, some more some less than the Ocean Sea, which in the present case may also be esteemed a Lake; since by that term I mean such Standing Waters as perpetually receive Rivers running into them, and have no Exite or Evacuation. The Number of these Lakes, in the known Parts of the World is exceeding small, and indeed upon Enquiry I cannot be certain there are in all any more than four or five, viz. first, The Caspian Sea; secondly, The Mare Mortuum or Lacus Asphaltites; thirdly, The Lake on which stands the City of Mexico, and fourthly, The Lake of Titicaca in Peru, which by a Channel of about fifty Leagues communicates with a fifth and smaller, call'd the Lake of Paria, neither of which have any other Exite. Of these the Caspian, which is by much the greatest, is reported to be somewhat less salt than the Ocean. The Lacus Asphaltites is so exceedingly Salt, that its Waters seem fully sated, or scarce capable to dissolve any more; whence in Summer-time its Banks are incrustated with great Quantities of dry Salt, of somewhat a more pungent nature than the Marine, as having a Relish of Sal Armoniac; as I was informed by a curious Gentleman that was upon the place. The Lake of Mexico properly speaking is two Lakes, divided by the Causways that lead to the City, which is built in Islands in the midst of the Lake, undoubtedly for its Security; after the Idea, tis probable, its first Founders borrowed from their Beavers, who build their Houses on Damms they make in the Rivers after that manner. Now that part of the Lake which is to the Northwards of the Town and Causways, receives a River of a considerable magnitude, which being somewhat higher than the other, does with a small Fall exonerate it self in the Southern part, which is lower. Of these the lower is found to be salt, but to what degree I cannot yet learn; though the upper be almost fresh. And the Lake of Titicaca, being near eighty Leagues in circumference, and receiving several considerable fresh Rivers, has its Waters, by the Testimony of Herrera and Acosta, so brackish as not to be potable, though not fully so salt as that of the Ocean; and the like they affirm of that of Paria, into which the Lake of Titicaca does in part exonerate itself, and which I doubt not will be found much saltier than it, if it were enquired into. Now I conceive that as all these Lakes do receive Rivers and have no Exite or Discharge, so 'twill be necessary that their Waters rise and cover the Land, until such time as their Surfaces are sufficiently extended, so as to exhale in Vapour that Water that is poured in by the Rivers; and consequently that Lakes must be bigger or lesser according to the Quantity of the fresh they receive. But the Vapours thus exhaled are perfectly fresh, so that the saline Particles that are brought in by the Rivers remain behind, whilst the fresh evaporates; and hence 'tis evident that the Salt in the Lakes will be continually augmented, and the Water grow saltier and saltier. But in Lakes that have an Exite, as the Lake of Genesaret, otherwise call'd that of Tiberias, and the upper Lake of Mexico, and indeed in most others, the Water being continually running off, is supply'd by new fresh river Water, in which the saline Particles are so few as by no means to be perceived. Now if this be the true Reason of the Saltness of these Lakes, 'tis not improbable but that the Ocean it self is become salt from the same Cause, and we are thereby furnished with an Argument for estimating the Duration of all Things, from an Observation of the Increment of Saltness in their Waters. For if it be observed what Quantity of Salt is at present contained in a certain Weight of the Water Water of the Caspian Sea, for example, taken at a certain Place, in the dryest Weather; and after some Centurys of Years the same Weight of Water, taken in the same place and under the same Circumstances, be found to contain a sensibly greater Quantity of Salt than at the time of the first Experiment, we may by the Rule of Proportion, take an estimate of the whole time wherein the Water would acquire the Degree of Saltness we at present find in it. And this Argument would be the more conclusive, if by a like Experiment a similar Encrease in the Saltness of the Ocean should be observed: for that, after the same manner as aforesaid, receives innumerable Rivers, all which deposite their saline Particles therein; and are again supplyed, as I have elsewhere shewn, by the Vapours of the Ocean, which rise therefrom in Atoms of pure Water, without the least admixture of Salt. But the Rivers in their long Passage over the Earth do imbibe some of the saline Particles thereof, though in so small a Quantity as not to be perceived, unless in these their Depositories after a long Tract of time. And if upon repeating the Experiment, after another equal Number of Ages, it shall be found that the Saltness is further encreased with the same increment as before, then what is now proposed as Hypotheticall would appear little less than Demonstrative. But since this Argument can be of no use to Ourselves, it requiring very great Intervals of time to come to our Conclusion, it were to be wished that the ancient Greek and Latin Authors had delivered down to us the degree of the Saltness of the Sea, as it was about 2000 Years ago: for then it cannot be doubted but that the Difference between what is now found and what then was, would become very sensible. I recommend it therefore to the Society, as opportunity shall offer, to procure the Experiments to be made of the present degree of Saltness of the Ocean, and of as many of these Lakes as can be come come at, that they may stand upon Record for the benefit of future Ages. If it be objected that the Water of the Ocean, and perhaps of some of these Lakes, might at the first Beginning of Things, in some measure contain Salt, so as to disturb the Proportionality of the Encrease of Saltness in them, I will not dispute it: But shall observe that such a Supposition would by so much contract the Age of the World, within the Date to be derived from the foregoing Argument, which is chiefly intended to refute the ancient Notion, some have of late entertained, of the Eternity of all Things; though perhaps by it the World may be found much older than many have hitherto imagined. Accounts of BOOKS. I. Linear Perspective, or a New Method of representing justly all manner of Objects, &c. By Brook Taylor, L. L. D. and R. S. Secr. 8vo. London, 1715. The Author of this Book, finding the Art of Perspective to be very imperfect in the Books that have hitherto been publish'd on that Subject, thought it worth his while to consider the whole matter anew; and from a careful Examination of the Principles this Art is founded upon, he has endeavoured to establish some Theorems, by means of which the Practice of it might be render'd more general and easy than has yet been done. In order to this, at first sight he found it necessary to make use of new Terms of Art; the old ones seeming not to