A Letter of Dr. Wallis, Dated Oxford, Sept. 6. 1697. Containing Some Additions to His Letter about Thunder and Lightning, and a Correction of His 109th Cap. of His Algebra

evident by her Declaration on her Death Bed) married and brought forth a Boy in the Two and Fiftieth Year of her Age, having Two Teeth in his Head. 10. Another Woman in Lewis, was Seven Years bringing forth a Child Bone after Bone, and all by the Fundament. 11. A Boy in the Isle of Skie, Aged Sixteen Years, has a Faculty of erecting his Ears at his Pleasure. There are several Towns in Skie, where the Sheep have no Marrow, all these Towns are Rocky, High, and very Windy. 12. The Inhabitants of St. Kilda, are every Summer infected with a Cough upon the Chamberlans Landing, which lasts for Ten or Twelve Days, and the usual Remedy for it is Giben drunk upon Brochan of Meal and Water. This Giben is the Fat of Sea Fowls preserved in the Stomach, a sove-raign Remedy for Coughs and Green Wounds. VII. A Letter of Dr. Wallis, Dated Oxford, Sept. 6. 1697. Containing some Additions to his Letter about Thunder and Lightning, and a Correction of his 109th Cap. of his Algebra. I find that in your Transactions Numb. 231. for the Month of August, you have Printed my Letter of July 26. If it had not been too late, I would have added, That, when I said, A Mixture of Sulphur and Fillings lins of Steel, with the admission of a little Water, will not only cause a great Effervescence, but will of itself break forth into an actual Fire; I said expressly, a little Water; because too much Water will hinder the Operation, or quench the Fire. Which I take to be the Case of the Bath-Waters, where Steel and Sulphur cause a great Effervescence, but no Flame. And the like of other Hot Springs. And I do not confine it to this particular Mixture; for the Chymists, I presume, may furnish us with divers others. And therefore I said, or somewhat equivalent. But I gave Instance of this for one. I would have added also, That the same Account may be given of Ætna (and other burning Mountains;) where the Mixture of Steel and Sulphur may give a Flame; which is oft attended with prodigious Explosions (and Earth-quakes) from great Quantities of Niter, as in springing a Mine. I shall also take this Occasion to rectify some Numbers which I find to have been mistaken in my Treatise of Algebra, at Cap. 109. which though they do not vitiate the Demonstration (which will hold as well when these be rectified) yet I think fit to correct them, that they may not give the Reader a trouble. In Algebrae meæ Cap. CIX. irrepserunt Numeri vitiosi. Qui quamvis summam Demonstrationis non evertant, sunt tam rectificandii. Propositum est, Datum Cubum (cujus latus ponatur = 1,) ita perforare, ut Cubus alter, æqualis, per foramen transeat. Quod cum pluribus modis fieri possit, hunc selegis. Intelligatur Cubus perforatus, Sphaeræ inscriptus; Cujus itaq; Diameter seu Axis erit (æqualis Diagonio Cubi) = √3. Cujus Polos occupent Cubi Angulus A, & huic oppositus latens. Reliquiæ sex Anguli Anguli BCDEFG, in planum per Centrum (Axi ad Angulos rectos) projiciantur. Non quod illi omnes sint in eodem plano; sed BDF sunt in plano superiori quod ab A (polo proximo) distat Axis triente; reliquiq; CEG, in plano huic parallelo quod tantundem distat ab oppotito polo latente. Sed omnes hi Anguli, demissis in planum ilud per centrum perpendicularibus projecti, formabunt in illo hexagonum regulare BCDEFG. Cui si intelligatur Circulus circumscriptus; non erit ille, Circulus Sphaerae maximus (quia puncta sic projecta non pertingunt ad extremum ambitum Circuli Sphaerae maximi per centrum;) sed qualis ille est qui per BDF, vel per CEG, transit. Cujus itaq; Diameter est \( \sqrt{\frac{8}{3}} \). Et PB \( = \sqrt{\frac{1}{6}} \). Et PG \( = \sqrt{\frac{2}{3}} \). Et BM \( = \sqrt{\frac{3}{2}} - \frac{1}{2} \). Et MQ \( = \sqrt{2} - \frac{1}{2} \sqrt{3} \). Cum itaq; MH \( = \frac{5}{2} = 0.500 \). (semilatus incumbentis Cubi transfuturi) minus sit quam MQ \( = \sqrt{2} - \frac{1}{2} \sqrt{3} = 0.548 + \); Manifestum est (facto foramine HIKL) transire posse cubum incumbentem, perforato aqualem. VIII. Account of Books. 1. Refraetio solis occidui in septentrionalibus oris jussu serenissimi ac potentissimi Principis Caroli II. Suecorum, Gothorum, Vandalorum, &c. Monarchae Clementissimi, circa Solstitium aestivum, 1695. aliquot observationibus Astronomicis detecta. Holmiae in 4°. Sweedish and Latin, and now Translated into English, and Printed for Ed. Castle next Scotland-Yard Gate by White-Hall, in 8°. In Chap. I. the Author, J. Bilberg, gives an Account of the King of Sweden’s Observation, which was, that being at Torneo in Westro-Bothnia, situated in 65°. 43'. Lat.