Dr Henry 07i the M eigne site of Anglesey. 155 



renders the whole completely air-tight. The acid is now to 

 be mixed with the water by frequently inverting and shaking 

 the cylinder. If the copper and zinc cylinders be connected 

 with the galvanometer, the battery will continue to act for a 

 day or two with the same energy as if the whole had been 

 left exposed to the air. As there is no room for the dis- 

 engagement of hydrogen, the oxygen of the water cannot 

 combine with the zinc to convert it into an oxide ; neverthe- 

 less chemical action goes on, and the zinc is dissolved in the 

 acid. From this experiment it is obvious that the oxidation 

 of the ?inc and the combination of nascent hydrogen with the 

 electric fluid, as Dr Bostock supposes, has nothing to do with 

 the production or transfer of the electricity which appears a.V 

 the surface of the zinc. The metal is still, however, dissolved 

 or reduced from a solid to a fluid state ; and as its capacity 

 for caloric has undergone a change, may not its capacity for 

 the electric fluid have also undergone a certain change ? 

 Hence it is possible that the true theory of galvanism may be 

 more intimately connected with that of latent heat than has 

 yet been supposed. Since the zinc is dissolved without the 

 assistance of oxygen from the water, it appears that the atoms 

 of the acid have combined with the pure brilliant atoms of the 

 metal, without the necessity of the metal being first converted 

 to an oxide. 



From the short view that I have taken of this interesting 

 subject, it appears that the electric theory is quite unfounded, 

 and that the chemical theory will require some modification 

 to embrace the facts contained in the last experiments. This 

 I shall not, however, attempt at present ; as my object in this 

 papei* is rather to demolish old fabrics and collect new mate- 

 rials, from which a more substantial edifice may be raised. 



Art. XVIII. — On the Magnesite discovered in Anglesey, 

 By William Henry, M. U. F. R. S., &c. Contained in 

 a Letter to Dr Hibbert, dated 5th Dec. 



When I showed you, a few weeks ago, a specimen of magne- 

 site which I had found in the autumn of 1828, in Anglesey, 



