1817.) Philosophical Transactions, 1816. 467 
prietors to convert it into asulphate of magnesia manufactory. The 
pyrites is roasted, and then left in a shade for some time, being 
occasionally moistened with water. It is then lixiviated. The 
copper is thrown down by means of iron, and the iron by means of 
magnesian lime-stone. The liquid is then filtered and concentrated 
sufficiently for the crystallization of the sulphate of magnesia. 
20. On the Formation of Fat in the Intestines of the Tadpole, and 
on the Use of the Yelk in the Formation of the Embryo in the Egg. 
By Sir E. Home, Bart. . 
The length of intestine in the tadpole, when compared with that 
of the animal, is greater than in any other creature. During this 
state a quantity of fat is deposited on the loins of the tadpole. When 
the taapole is changed into a frog, the intestine becomes much 
shorter, and the fat has disappeared. The author conceives that the 
use of the great length of intestine in these animals was the forma- 
tion of fat, and that the fat was deposited to assist in the subsequent 
transformations of the animal. The ovum of the frog contains no 
yolk. 
21. On the Structure of the Crystalline Lens in Fishes and 
Quadrupeds, as ascertained by its Action on polarized Light. By 
Dr. Brewster. 
The author concludes from his experiments that the central 
nucleus and the external coat of the lens are in a state of dilatation, 
while the intermediate coats are in a state of contraction. 
22. Some further Account of the Fossil Remains of an Animal 
of which a Description was given to the Society in 1814, By Sir 
E. Home, Bart. 
From specimens in the possession of the Rev. Mr. Buckland and 
Mr. Jobnson, the author considers it as established that the animal 
in question was a fish, but quite different in its structure from any 
known species. 
23. Further Observations on the Feet of Animals whose pro- 
gressive Motion can be carried on against Gravity. By Sir E. 
Home, Bart. 
The author gives further examples of the structure described in 
his former paper. 
24. A new Demonstration of the Binomial Theorem. By Thomas 
Knight, Esq. 
25. On the Fluents of Irrational Functions. By Edward Ffrench 
Bromhead, Esq. M. A. 
