Proceedings of the Royal Society. 279 
of June, in a lake three miles from Mexico, at an elevation of 
8,000 feet above the level of the sea; the usual temperature of the 
lake is 60°, and they are in such abundance as to form a principal 
article of food of the peasantry. 
By the assistance of a series of annexed drawings by Mr. Bauer, 
Sir Everard fully describes the male and female organs of these 
animals, and is enabled to decide that they are a full grown and 
perfect tribe. ‘“ The attack therefore,” says the author, ‘‘ made 
upon Mr. John Hunter’s sagacity, by M. Rusconi, in his work Sur 
les amours des Salamandres aquatiques, retorts upon himself.” 
On the Effects of Temperature on the Intensity of Magnetic Forces, 
and on the Diurnal Variation of the Terrestrial Magnetic Inten- 
sity. By 8. H. Christie, Esq. M. A. 
The details of the author’s experiments upon the above subjects are 
given in an extended series of tables. Commencing with a tem- 
perature —3° F. up to 127°, Mr. Christie found, that as the 
temperature of the magnets increased, their intensity diminished, 
in direct contradiction to the notion of destroying magnetism by 
intense cold. From a temperature of 80° the intensity decreased 
rapidly as the temperature increased, and at above 100°, a portion 
of the power of the magnet was permanently destroyed. 
Additional Experiments and Observations on the Application of 
Electrical Combinations to the Preservation of the Copper Sheathing 
of Ships, and to other Purposes. By Sir H. Davy, Bart. P.R.S 
Since his former communication, the President has had an oppor- 
tunity of pursuing his researches upon the above subjects, upon an 
extended scale, and with results perfectly conclusive and satis- 
factory. He found that sheets of copper defended by from +35 to 
azhy part of zinc or iron, exposed for many weeks to the full flow of 
the tide in Portsmouth harbour, suffered no corrosion, and that 
even -y'y¢ part of cast iron exerted great protecting influence, 
