600 Intelligence and Miscellaneous Articles. 



This salt, according to M. Peligot, consists of 

 Az 

 O 3 



4PbO 

 HO 



"6167-5 100- 



and he calls it a basic nitrite of lead, as determined by Berzelius 

 and Chevreul. 



Considered as a sub-hyponitrite of lead, its composition will be 

 nearly — 



One equivalent of hyponitrous acid. . 38 7*7 



Four equivalents of protoxide of lead 448 90'5 



One equivalent of water 9 1*8 



"495 100- 



Ann. de Chim. et de Phys., Mai 1841. 



INQUIRY RESPECTING A MS. AT OXFORD, REFERRED TO BY 

 MR. RUTHERFORD IN HIS PAPER ON THE RATIO OF THE 

 DIAMETER OF A CIRCLE TO ITS CIRCUMFERENCE. BY J. O. 

 HALLIWELL, ESQ., M.A., F.R.S. 



To the Editors of the Philosophical Magazine. 

 Gentlemen, 

 In an interesting paper by Mr. Rutherford on the ratio of the dia- 

 meter of a circle to its circumference, just printed in the Phil. Trans.*, 

 a reference is made to a manuscript at Oxford, in which the numerical 

 approximation is carried as far as 152 places of decimals, but no press- 

 mark is given to the manuscript ; and, after a careful search through 

 all the printed catalogues, I have not been able to find an account of 

 any manuscript at all likely to contain such a calculation. There 

 are very few scientific manuscripts in the Bodleian Library of a later 

 date than the fifteenth century, and it is quite impossible that the 

 approximation could have been carried so far at that early period. 

 If Mr. Rutherford possesses a reference to the manuscript in ques- 

 tion, or any clue to it, he would confer an obligation on me, and I 

 have little doubt on many others, if he would kindly communicate it 

 to your Magazine, and it is very probable the manuscript may con- 

 tain other matters worthy of notice. At all events, it would be sa- 

 tisfactory to ascertain the date of the manuscript. 



I am, Gentlemen, your obedient servant, 

 Dec. 17th. J. O. Halliwell. 



* [Of which an abstract will be found at p. 561 of the preceding volume. 

 — Edit.] 



INDEX 



