_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 _A Translation of Part of Monsieur _Fontenelle's_ Preface to the Memoirs of the Royal Academy at _Paris_, in the Year 1699. treating of the Usefulness of Mathematical Learning._ But to what purpose should People become fond of the Mathematicks and Natural Philosophy. Of what use are the Transactions of the Academy? These are common Questions, which most do not barely propose as Questions; and it will not be improper to clear them. People very readily call useless, what they do not understand. It is a sort of Revenge; and as the Mathematicks and Natural Philosophy are known but by few, they are generally look'd upon as useless. The reason of this is; because they are crabbed and not easily learnt.