C iv 3 
XVII. General Theorems, chiefly Porisms, in the higher Geo - 
metry. By Henry Brougham, Jun . Esq. Communicated by 
Sir Charles Blagden, Knt. F. R. S. p. 378 
XVIII. Observations of the diurnal Variation of the Magnetic 
Needle , in the Island of St. Helena ; with a Continuation of 
the Observations at Fort Marlborough , in the Island of Su- 
matra. By John Macdonald, Esq. In a Letter to the Right 
Hon. Sir Joseph Banks, Bart. K. B. P. R. S. p. 397 
XIX. On the Corundum Stone from Asia. By the Right Hon. 
Charles Greville, F. R. S. p. 403 
XX. An Inquiry concerning the chemical Properties that have 
been attributed to Light. By Benjamin Count of Rumford, 
F. R. S. M. R. I. A. p. 449 
XXI. Experiments to determine the Density of the Earth. By 
Henry Cavendish, Esq. F.R.S. and A.S. p. 469 
XXII. An improved Solution of a Problem in physical Astro- 
nomy ; by which , swiftly converging Series are obtained, which 
are useful in computing the Perturbations of the Motions of 
the Earth , Mars, and Venus, by their mutual Attraction. To 
which is added an Appendix, containing an easy Method of 
obtaining the Sums of many slowly converging Series which 
arise in taking the Fluents of binomial Surds, &c. By the 
Rev. John Hellins, F.R. S. Vicar of Potter s Pury, in North- 
amptonshire. In a Letter to the Rev. Nevil Maskelyne, D. D. 
F. R. S. and Astronomer Royal. p. 527 
XXIII. Account of a Substance found in a Clay -pit ; and of 
the Effect of the Mere of Diss, upon various Substances im- 
mersed in it. By Mr. Benjamin Wiseman, of Diss, in Nor- 
folk. Communicated by John Frere, Esq. F. R. S. With an 
Analysis of the Water of the said Mere. By Charles 
