430 Miscelianeous Intelligence. 



,12. Dilated Caoutchouc Bottles. — Mr. Foister has shewn, that 

 caoutchouc bottles may be expanded, until so thin and large as 

 to answer many purposes of bladders, in philosophy and the arts. 

 His process is to condense air into the caoutchouc which gradually 

 forms the appearance of a blister at the bottom of tlie bottle, and 

 which, extending, at last includes the whole. In this way the 

 bottles have been made 6 and 7 inches in diameter; and by care, 

 Mr. F. thinks may be made thin enough for balloons. When 

 rubbed on warmed paper, these globes become very strongly 

 electrical. — Phil. Mag. lix. 263. 



13. Prize Question. — The Royal Academy of Sciences has pro- 

 posed the following prize subject for 1824. 



1. To determine, by multiplied experiments, the density ac- 

 quired by liquids, and particularly by mercury, wafer, alcohol, 

 and ether, under pressure equal to the weight of many atmo- 

 spheres. 



2. To measure the effects of the heat produced by these com- 

 pressions. 



The prize is a medal of gold, value 3000 francs. The memoirs 

 to be sent in before January 1, 1824. 



§ 2. Ei-ECTRiciTY, Magnetism. 



14. Pyro-Electncit]! of Minerals. — M. L'Abbe Haijy has re- 

 marked, with regard to the electricity produced in certain crystals 

 by an alteration of temperature, tiiat it is of two kinds. The 

 accidental circumstances which led to the discovery took place 

 whilst he was examining some crystals of the oxide of zinc, from 

 Limbnurg, near Aix-la-Chapelle, and fragments of the acicular 

 variety of the same mineral from Brisgau. Having placed a piece 

 of one of these substances in a very cold window for a fe\Y 

 moment*^, it was found on examination to be electrical. Its poles 

 were ascertained, and the mineral then placed in a milder tem- 

 perature, when the electricity soon became nul; but being 

 approached to a fire-place, the power was greatly renewed, but 

 the poles were inverted. 



These results have been verified by M. Haiiy on other crystals, 

 especially those of the tourmaline. In taking them for examples, 

 he has endeavoured to bring under one point of view all that 

 passes with respect to them in the interval comprised between the 

 limits of temperature, beyond which the electric action disappears 

 without return. He has given the name of ordinari/ electricity to 

 that produced by heat, and extraordinary electricity to that pro- 

 duced by cold. If, therefore, commencing at the point where 

 the exc^'ss of heat destroys in the tourmaline the effects of 

 t^he ordinary electricity, that mineral be left to cool it will 

 %o{Y\ oive sig:\s of ordinary electricity. The action of 



