Chemical Science. 421 



which I communicated in my letter published in April, in the 

 Anthologia for this year, obliges me to make known, on the same 

 subject, some observalions not less interesting than the former. 

 From the time when I first observed this phenomenon, I have 

 adhered to the idea, that the electric state acquired by the glass 

 might depend on the evaporation of the aqueous film, which 

 always covers its surface. Therefore, to remove so doubtful a 

 fact from my observation, I endeavoured to perform the experi- 

 ment in a different manner. After having frequently touched a 

 flat piece of glass with a trial plane, without perceiving any sensible 

 developement of electricity, I heated it strongly that it might get 

 rid of the moisture adhering to it ; and having then left it to get 

 dry under a bell, which had been previously dried by heat and by 

 muriate of lime, I then frequently made trial with the same plane, 

 and never did I see any electricity developed by it, which, however, 

 would have quickly happened if the plate had been abandoned for 

 a few moments to the direct action of the solar rays. Yet, how- 

 ever frequently I saw the evaporation of the stratum of water which 

 covered it, excluded from the causes of rendering electric the plate 

 of glass exposed to the sun's rays, still the touching of the glass 

 plate with the trial plane did not appear to me a method free from 

 all exception, it being too easy to develop electricity either by 

 pressure or by any friction. I wished, therefore, to vary my method 

 of experiment, so as not to have my observation, if correct, lie open 

 to denial. Having added to the condensing plate a metallic wire, 

 soldered at the extremity to a large disc of brass, I placed upon 

 this a glass plate, and made the sun's rays fall upon it, without 

 their touching the box of the electrometer. I then perceived the 

 leaves diverge sensibly, and having raised the plate, and then the 

 collecting plate, I observed, as was very natural, the divergence 

 increase. In this way, the cause of the electric state of the glass 

 exposed to the sun's rays appeared to me reduced exclusively to 

 the power of those rays. If these new statements appear to you 

 interesting to science., they are at your disposal." — Carlo Matteucci, 

 Forli, August 13, 1829. 



28. — On a new Oxide of Manganese. By Mr. Phillips. — Mr. R. 

 Phillips, whilst engaged in examining the oxide of manganese from 

 Warwickshire, was enabled to distinguish certain parts of it from 

 other oxides with which it had been confounded, and to shew that 

 it was a new compound of the metal with oxygen. He has called 

 it Varvacite. In general appearance, and many ot its properties, 

 it so closely resembles the native peroxide, that there can be little 

 doubt but that it has frequently been mistaken for it. 



This mineral has a grey colour, the tint of which is not remark- 

 ably different from that of the well-known crystallized peroxide ; 

 it is, however, less brilliant. It is much harder than the peroxide, 

 does not soil the fingers so much, and is lighter in the proportion 



