VOt. VIII.] PHILOSOPHICAL TRANSACTIONS. 103 



will be CB = BA. Bisect the semi-axis AR in Q; then Q will be the focus, 

 and QB will be the space required. Now QB is half CR, because of the equals 

 AQ, QR, and AB, BC; that is, half the excess of the secant of the arc ER 

 above the radius. Therefore if the arc ER be, for example 9 degrees, then 

 AC will be 101246, and B = vo%Vo6 of AR. 



Account of Four Boohs ^ N° 97, p. 6 127. 



I. Tracts, consisting of Observations about the Saltness of the Sea: An 

 Account of a Statical Hygroscope and its Uses ; with an Appendix on the Force 

 of the Air's Moisture; and a Fragment on the Natural and Preternatural State 

 of Bodies: By R. Boyle, Esq. to which is prefixed a Sceptical Dialogue on the 

 Positive or Privative Nature of Cold. By a Member of the R. S. London, 

 1673, in 8vo. 



This very long and particular title, and the circumstance that the book is in 

 the possession of all philosophers, make it unnecessary to give any farther 

 account of it. 



II. Principia et Problemata aliquot Geometrica, ante desperata, nunc breviter 

 explicata et demonstrata; Auth. T. H. Malmesburiensi. Lond. An. 1673, 

 in 4to. 



The famous author of this tract, (Mr. Hobbes), haying entertained the 

 reader with some remarks concerning the subject, the principles and the method 

 of mathematics, and with his doctrine of ratio, as also his sense of algebraical 

 operations, with two chapters of square figures, square numbers, and angles j 

 undertakes to confirm his former doctrine ; 1. Of the ratio of the circumference 

 to the radius of a circle; 2. Of mean proportionals ; 3. Of the ratio of a square 

 to the quadrant of a circle inscribed in it; 4. Of solids and their superficies: 

 to which last he subjoins another method of demonstrating solids and their 

 superficies by their efficient causes.. Which done, he concludes the book with 

 a discourse touching demonstrations; the principal and most frequent cause of 

 fallacies in the mathematics; and the notion of the word Infinite. Complaining 

 very much, that geometry has received its greatest prejudice from those, that 

 discourse of a line without latitude; that take the side of a square for the root of 

 a number ; that understand not the true nature of ratio ; and that speak un- 

 favourably of Infinity! The whole being chiefly directed against Dr. Wallis. 



III. An Idea of a Phytological History propounded; with a Continuation of 

 the Anatomy of Vegetables, particularly prosecuted upon Roots ; and an Ac- 

 count of the Vegetation of Roots grounded chiefly thereupon. By Nehemiah 

 Grew, M. D. and F. R. S. London, 1673, in 8vo. 



This learned and inquisitive author, after the publication of his first endea- 



