A Discourse concerning the Proportional Heat of the Sun in all Latitudes; with the Method of collecting the same, as it was read before the Royal Society in one of their late Meetings, by Mr. E. Halley. 256 Concerning the Distance of the Fixed Stars, by the Honourable Fran. Roberts, Esq; F. R. S. 265 Mr. Isaac Newton's Theory of the Moon. 268 An estimate of the Degrees of the Mortality of Mankind, drawn from Curious Tables of Births and Funerals at the City of Breslaw; with an Attempt to ascertain the Price of Annuities upon Lives, by Mr. E. Halley. 280 A Discourse concerning Gravity, and its Properties, wherein the Descent of Heavy Bodies, and the Motion of Projects is briefly, but fully handled: Together with the Solution of a Problem of great Use in Gunnery, by Mr. E. Halley. 302 A Proposition of General Use in the Art of Gunnery, shewing the Rule of laying a Mortar to pass, in order to strike any Object above or below the Horizon, by Mr. E. Halley. 326 A Discourse concerning the Measure of the Air's Resistance to Bodies moved in it. By the Learned John Wallis, S. T. D. and F. R. S. 332 An Instance of the Excellency of the Modern Algebra, in the Resolution of the Problem of finding the Foci of Optick Glasses universally. By Mr. E. Halley, S. R. S. 348 Appendix An Analytical Resolution of certain Equations of the 3d, 5th, 7th, 9th Powers, and so on ad Infinitum, in finite Terms, after the manner of Cardan's Rules for Cubicks. By Mr. A. Moivre, F. R. S. 365 A Discourse concerning the Action of the Sun and Moon on Animal Bodies; and the Influence which this may have in many Diseases. By Richard Mead, M. D. F. R. S. 371

Miscellanea Curiosa.

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An Estimate of the Quantity of the Vapours raised out of the Sea derived from Experiment: Together with an Account of the Circulation of the watry Vapours of the Sea, and of the Cause of Springs, presented to the Royal Society. By Mr. E. Halley, F. R. S.

THAT the Quantity of Aqueous Vapours contain'd in the Medium of the Air, is very considerable, seems most evident from the great Rains and Snows which are sometimes observ'd to fall, to that degree, that the Water thus discharg'd out of the Interstices of the Particles of Air, is in weight a very sensible part of the incumbent Atmosphere: But in what proportion these Vapours rise, which are the Sources not only of Rains, but also of Springs or Fountains (as I design to prove) has not, that I know of, been any where well examin'd, tho' it seem to be one of the most necessary Ingredients of a Real and Philosophical Meteorology, and, as such; to deserve the Consideration of this Honourable Society. I thought it might not be unacceptable to attempt by Experiment to determine the Quantity of the Evaporations of Water, as far as they arise from Heat, which upon Trial succeeded as follows.

We took a Pan of Water, about 4 inches deep, and 7 Inches ⁹⁄₁₀ Diameter, in which we placed a Thermometer, and by means of a Pan of Coals, we brought the Water to the same degree of Heat, which is observed to be that of the Air in our hottest Summer; the Thermometer nicely shewing it: This done, we affixed the Pan of Water, with the Thermometer in it, to one end of the Beam of a Pair of Scales, and exactly counterpois'd it with weights in the other Scale; and by the application or removal of the Pan of Coals, we found it very easie to maintain the Water in the same degree of Heat precisely. Doing thus we found the weight of the Water sensibly to decrease; and at the end of two hours we observed that there wanted half an Ounce Troy, all but 7 grains, or 233 grains of Water, which in that time had gone off in Vapour; tho' one could hardly perceive it smoke, and the Water were not sensibly warm. This Quantity in so short a time seem'd very considerable, being little less than 6 ounces in 24 hours, from so small a Surface as a Circle of 8 inches Diameter. To reduce this Experiment to an exact Calculus, and determine the thickness of the Skin of Water that had so evaporated, I assume the Experiment alledg'd by Dr. Edward Bernard to have been made in the Oxford Society, viz. That the Cube-foot English of Water weighs exactly 76 Pounds Troy; this divided by 1728, the number of Inches in a Foot, will give 253⅓ grains, or ½ ounce 13⅓ grains for the weight of a Cube-inch of Water; wherefore the weight of 233 grains is ²³³⁄₂₅₃ or 35 Parts of 38 of a Cube-inch of Water. Now the Area of the Circle whose Diameter is 7⁹⁄₁₀ Inches, is 49 square Inches: by which dividing the Quantity of Water evaporated, viz. ³⁵⁄₃₈ of an Inch, the Quote ³⁵⁄₁₈₆₂ or ¹⁄₅₃ shews that the thickness of the Water evaporated was the 53d part of an Inch; but we will suppose it only the 60th part, for the Facility of Calculation. If therefore Water as warm as the Air in Summer, exhales the thickness of a 60th part of an Inch in two hours from its whole Surface, in 12 hours it will exhale the ⅒ of an Inch; which Quantity will be found abundantly sufficient to serve for all the Rains, Springs, and Dews; and account for the Caspian Sea,