94 Gulvanifm. 



with a real deflagration in the atmofpheric air. This laft 

 .effect always takes place in oxygen gas, and has a perfect re- 

 femblance to the inflammation which iron experiences when 

 immerfcd in that gas after a piece of lighted tinder has beer> 

 attached to it. 



u In the air the wire often becomes red, fufes into glo- 

 bules is vaporized at the fame time that it emits bright 

 fparfc*, and the poTtibh of the wire next, (b that which has 

 been fufed becomes brittle like the oxide of that metal. In- 

 fread offbrtnm;£tne communication with wires, if the branches 

 of a pair of lei'Iars (pair de afeaicx) be employed, as is fre- 

 quently done Ibr trying the piles, there is excited at the ex- 

 tremity of the one which touches the zinc, a bright fpark, 

 accompanied with a decrepitation. 



" The communicating wire when immerfed in hydrogen 

 f:ts, and in carbonic gas > is alfo luminous ; but it is only 

 ivuVels or meaudefeence, as the wire does not change colour, 

 and Hill retains its ductility. This incandefeehee is mani- 

 Jfefied when the experiment is made under mercury with gas. 

 and conductors very dry; the effect therefore is not owing to 

 the water decomposed on the conducting wires, but to twe* 

 eaufes united. 



£( The motion of the galvanic fluid reddens the iron; and 

 the air, particularly the oxygen gas in which it is immerfed^ 

 inflames it, and burns with decrepitation or deflagration.- 



" Small parcels of zinc placed on the laft plate, and touched 

 bv a brafs wire communicating with the lower plate, are 

 fometimes reduced to powder or into fmok'e at the moment 

 of contact, and a very fenfible decrepitation is then produced,, 

 but without inflammation. This phenomenon is not focon- 

 ftant as the inflammation of the iron wire. 



66 Tins inflammation does not take place, unlefs the plates 

 of copper and zinc be from 10 to j\ inches, at the lead, in 

 diameter. 



" It is moft remarkable, that piles compofed of thefe large 

 plates give only feeble fhocks, and effect onlv very {lowly 

 the decomporition of water; while if each of the plates be 

 divided into four, and it* thefe fmall plates be placed one 

 above the other, with pieces of cloth moiftened with an am- 

 moniacal folution interpofed between each pair, they produce 

 a commotion four times as ftrong, and a much fpeedier de- 

 compofition of water, without exciting an inflammation of 

 the air. Thus, the galvanic power which ignites metals rife? 

 in a ratio different from that which decompofes water, and 

 excites mufcular movements. 



*' The Srft of thefe powers follows the fizc of the metallic 



plates 



