491 Royal Society. 



Letter from Mr. William Sewell to Everdrd Home, Esq,, 

 F.R.S. — G. A numerical Table of elective Attractions ; with 

 Remarks on the Sequences of double Decompositions. By 

 Thomas Young, M.D. For. Sec. R.S. — 7. Account of the 

 Dissection of a Human Foetus, in which the Circulation of 

 the Blood was carried on without a Heart. By Mr. B. C. 

 Brodie. Communicated by Everard Home, Esq., F.R.S. — 

 8. On the Origin and Formation of Roots. In a Letter from 

 T. A. Knight, Esq., F.R.S., to the Right Hon. Sir Joseph 

 Banks, Bart., K. B. P.R.S.— 9. On the Nature of the inter- 

 vertebral Substance in Fish and Quadrupeds. By Everard 

 Home, Esq., F.R.S. 



June I. — The president in the chair. The conclusion of 

 Dr. Henry's paper on the decomposition of ammonia was 

 read. The result of the author's present experiments led him 

 to perceive some errors in those of his preceding paper, 

 and to conclude that the oxygen which he had disengaged 

 from ammonia by electrization was derived from other 

 bodies, and not from the ammonia; consequently that am- 

 monia should not yet be considered as an oxide. 



Mr. Davy read some remarks on Dr. Henry's experi- 

 ments, which tended to prove that the composition of fcw» 

 monia cannot be ascertained till the nature of nitrogen is 

 determined. Dr. H. thought the proportion of hydrogen in 

 ammonia, as determined by Mr. Davy, rather low, and es- 

 timated it at 72 hydrogen and 28 nitrogen, instead of 74 

 hydrogen and 26 nitrogen ; but Mr. D. having repeated his 

 experiments, found them very nearly correct, and took 

 73 — 27 as the truth. 



An ingenious paper by the Rev. Mr. Lax, professor of 

 astronomy at Cambridge, was read, on the means of gra- 

 duatmcf and correcting mathematical instruments. The au- 

 thor uses Carey's semi- circle of a foot diameter, corrects it 

 by microscopes and observations, and adjusts it so as to 

 counteract the expansion and contraction by change-of tem- 

 perature. 



j une Q. — Dr. Wollaston read a paper proving the identity 

 of columbium and tantalium, the former discovered by Mr. 

 Hatchett,, the latter by the Swedish chemist Ekeberg. Dr. 



W. pro- 



