504? SCIENTiriC NEWS. 



the two gafes included in the fyrlnge of an air-gun. The 

 compreflion which forces the particles of gas together, caufes 

 them to give out a fufficient quantity of heat to fet them on 

 fire. Some caution is requifiie in repeating this experiment, 

 which is not without danger. Out of tliree times that M. 

 Biot made it, there were two in which the brafs cap of the 

 pump and the barrel itfelf, which was iron, were broken by 

 the exploiion. 



300' 



Malleability of Zinc. 



Zinc Is malleable A VERY curious and ufeful difcovery has been made by 

 while heated be- Melfrs. Charles Hobfon and Charles Sylvefter. both of Shef- 

 ^^J» »»«>* ^"'^ field, that zinc is in fad a malleable metal. The laminability 

 ""^ " of this metal to a certain confiderable degree, has long been 



known; but it was not fufpefted that it is capable of being 

 forged and drawn into wire. They have found that at a tem^^ 

 perature between 210^ and 300*=* of Fahrenheit zinc yields to 

 the hammer, and alfo that it may be wire-drawn or laminated 

 by keeping it at this temperature during the mechanical oper- 

 ation. An oven or a hollow metallic veflcl kept at a due heat 

 may be ufed for the piece?, in the fame manner as the Smith's 

 forge is ufed for iron and fteel. It appears that the zinc, after 

 having been thus annealed and wrought, continues foft, flex- 

 ible and extenfible, and does not return to its former partial 

 brittlenefs, but may be bended and applied to the ules for 

 which zinc has hitherto been thought unfit, fuch as the fabri- 

 cation of velTels, the flieathing of fliips, and numerous other 

 important applications. I have feen a chafed or ftamped figure 

 raifed at one flroke in thin zinc ; which is, I think, as much 

 elevated as it could have been in copper.* 



Palladium. 



palladium. BY a letter from Meflrs. Knight, of Fofter-Iane, I am in- 



formed that the new metal, palladium, may be purchafed at 

 their warehoufe. 



Xrratum cor- 

 eited. 



Mr. GREGORY begs leave to corre6l a miftake which 

 occurs in his paper on horfe-powers, occafioned by his inad- 

 vertently copying from fome of his former obfervationson that 

 fubjed the fradion f inftead of | for the approximate value of 

 the exponent n: this makes a change in the refults of the com- 

 putation at page 148; for (9-3)"? : (9-4.4)^: : 130: 80-58, 

 or nearly 80 J lb. inftead of 7 If, as there given. He alfo 

 points out a prefs error at p. 153, where the fymbols of mul- 

 tiplication in each of the theorems Ihould have been figns of 

 addition. 



* The inventors have obtained a patent. 



