332 



The oxide of lead, which had been deprived of its arsenic acid by 

 the potash, was then dissolved in nitric acid, and precipitated by 

 sulphate of soda in the state of sulphate of lead, from which the 

 quantity of lead in the ore proved to be 69f per cent. 



Mr. Gregor has found only one specimen in which the proportion 

 of lead to the acid was materially different. In this instance the 

 oxide of lead was 71 '45, and the acid 23-88, instead of being, as 

 before, 694 and 26-jV 



Beside these ingredients, the ore also contains a portion of mu- 

 riatic acid ; and the author has also detected small but variable pro- 

 portions of iron and silica. 



The quantity of muriatic acid was ascertained by solution of the 

 ore in nitric acid, and precipitation as usual by nitrate of silver. 

 But Mr. Gregor found it necessary to take certain precautions ; for 

 if the solution be made with much heat, part of the muriatic acid is 

 lost by boiling ; and if the solution be too concentrated, an arseniate 

 of silver is precipitated along with the muriate, and will then require 

 to be separated, either by solution of it in nitric acid, or by means 

 of its insolubility in pure ammonia, which dissolves the muriate. 



In order to determine decisively the nature of the principal acid 

 present in this ore, Mr. Gregor decomposed a portion by sulphuric 

 acid, and, after evaporation of the fluid poured off, reduced a part of 

 the acid upon charcoal. Part was dissolved in water, and precipitated 

 titanium from sulphate of titanium ; part was neutralized with soda, 

 and occasioned a brick-coloured precipitate from nitrate of silver, and 

 a reddish yellow precipitate from nitrate of mercury. 



From the whole of the expeiiments detailed in the paper, the au- 

 thor concludes that 100 parts of the ore contain 69'76 oxide of lead, 

 26'40 arsenic acid, 1*58 muriatic acid; and that the silica and oxide 

 of iron are not essential to its composition. 



An anatomical Account of the Squalus maximus (of Linnaeus), which 

 in the Structure of its Stomach forms an intermediate Link in the 

 Gradation of Animals between the Whale Tribe and Cartilaginous 

 Fishes. By Everard Home, Esq. F.R.S. Read May 11, 1809. 

 [Phil. Trans. 1809, p. 206.] 



The fish described in this account was caught in a herring-net at 

 Hastings, from whence such parts as were more particularly deserving 

 of notice were brought to London for further examination. 



It was a male, thirty feet six inches long, and nine feet broad, from 

 the tip of the dorsal fin to the middle line of the belly. 



The skin was of a light slate-colour, and though as rough as a 

 new file in the direction from the tail to the head, yet as smooth as 

 satin in the opposite direction. 



The mouth was about five feet wide, with six rows in each jaw of 

 small conical teeth, rather curved inwards. 



The nostrils were placed on the edge of the upper lip. 



The eyes very small, with pupils perfectly round. 



