INDEX. 
page 
Pond, John, Esq. On the parallax of the fixed stars in 
right ascension, - - - 481 
Poppy , corn, experiments on its colouring matter, 115 
Presents, a list of those made to the Royal Society from 
November 1817, to June 1818, - 519 
Prochaska, his account of experiments on the brain, 
when subjected to minute microscopical observations, 
noticed, - 177 
Prout, William, M. D, A description of an acid prin- 
ciple prepared from the lithic or uric acid, - 420 
Purpuric acid, a name given to an acid principle prepared 
from the lithic or uric acid, - - 421 
Purpurates, a name given to the compounds of the pur- 
puric acid with different bases, - 423 
R 
Rennie, George, Esq. An account of experiments made 
on the strength of materials, - - 118 
Rings or isochromatic curves, on the form of them, and on 
the nature of the tints in crystals with more than one 
axis, - - 22 6 
S 
Sap-green, some facts respecting the colour of this pigment, 1 16 
Seppings, Robert, Esq, On the great strength given to 
ships of war by the application of diagonal braces, 1 
Serpents, of their urinary organs and urine, - 303 
- — — on the structure of their poisonous fangs, 471 
Skiddazv a geometrical admeasurement of that mountain, 395 
Smith, Thomas, Esq, On the structure of the poisonous 
fangs of serpents, - 471 
Smithson, James, Esq. A few facts relative to the co- 
louring matter of some vegetables, - 110 
Stars, clusters oj j of the assumed semblance of them, when 
seen through telescopes that have not light and power 
sufficient to show their nature and construction, 463 
- — on their distance, - - 430 
— a series of observations upon them, from 
which the order of their profundity in space is deter- 
mined, - - - - 431 
Stars, jixcd, on the parallax of some of them, - 275 
— on the different methods of constructing a ca- 
talogue of them, - - 405 
