CONTENTS. 
XV. On a new principle of constructing His Majesty's Ships of 
War. By Robert Seppings, Esq. one of the Surveyors of His 
Majesty's Navy. Communicated by the Right Hon. Joseph 
Banks, Bart. K. B. P, R. S, page 285 
XVI. Remarks on the employment of Oblique Riders, and on other 
alterations in the consti'uction of Ships. Being the substance of 
a Report presented to the Board of Admiralty, with additional 
demonstrations and illustrations. By Thomas Young, M. D. 
For. Sec. R. S. ' p. 303 
XVII. Some further Observations on Atmospherical Refraction. 
By Stephen Groombridge, Esq. F. R. S. p. 337 
XVIII. Propositions containing some Properties ^Tangents to 
Circles; Trapeziums inscribed in Circles, and non- 
inscribed. Together with Propositions on the Elliptic Represen- 
tations of Circles, upon a plane surface, by Perspective. 
By Richard Hey, LL. D.; late Fellow of Sidney Sussex and 
Magdalen Colleges, in the University of Cambridge. Commu^ 
nicated by the Rev. Edward Balme, M. A. F. R. S. p. 34,8 
XIX. On new Properties of light exhibited in the optical Phe- 
nomena of Mother of Pearl, and other Bodies to which the 
superficial structure of that Substance can be communicated. By 
David Brewster, LL.D. F. R. S. Edin. and F.S.A. Edin. 
In a Letter addressed to the Right Hon. Sir Joseph Banks, 
Burt. K. B. P. R. S. p. 397 
