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On the Generation of Statical Electricity. 101 
tion, requiring frequent renewal ; and the quantity of electricity 
evolved, soon being but little more than that capable of being 
produced by the amalgam itself. The amalgam, in case the sul- 
phuret is employed, acts principally, by serving as a metallic com- 
munication to convey off the negative electricity, as rapidly as 
generated. ‘Tin or copper filings answer the same purpose, 
nearly as well as the amalgam. 
Hence the common amalgam has been sche as the most 
suitable material, on account of the quantity of electricity pro- 
duced, as well as its ease of application; and, when properly ap- 
plied, the valuable steadiness of its action. Its composition is but 
of little importance, equal parts, by weight, of zinc, tin, and mer- 
cury, answering every purpose. The zinc and tin are to be melt- 
ed together, the mercury then added, and the melted mass pour- 
ed into a wooden box, and agitated violently until cool; then it 
is to be still further reduced to a fine powder, by being rubbed in 
a mortar. The various results obtained by different electricians, 
each recommending a new proportion of ingredients, appear to 
have been caused by the different conducting powers of the cush- 
ions of the rubbers employed; they having failed, probably, in 
each case to connect the metallic faces with the earth. 
It will be observed that the oxides of zinc, tin and mercury, 
yield but a small comparative quantity of electricity ; hence the 
necessity of frequently renewing the amalgam of the rubbers, 
constructed after the ordinary method. The combination of mer- 
cury with the common metals, being rapidly oxidized by reason 
of the galvanic action, shows the reason why “amalgams con- 
taining much mercury are of transient and variable action.”* 
It is probable that pure mercury, if it were possible to apply it, 
so as to cause as much friction between its particles and the sur- 
face of glass as takes place with other metals, would surpass all 
other substances in its effective capabilities. This, however, is 
impossible as long as it continues fluid, on account of the mobility 
of its particles; and this mobility constitutes its chief value, by 
allowing a more perfect contact with the glass; hence its maxi- 
mum effect can be approximated to, only by rendering it semi- 
fluid, in forming an amalgam. 
The number of rubbers to be employed demands some atten- 
tion, and at the same time the action of the double rubbers, of 
. * Singer’s Treatise on Electricity, page 52. 
