[ T 39 ] 
The eafy ignition of the fait in a flight heat 
being thus afcertained, there is no room to doubt 
that the foregoing phenomena are produced in 
the following manner. 
The acid of the liquor, which moiftened the 
fait, quits the copper to unite with the tin, leav- 
ing the water to be imbibed by the contiguous fait 
of copper, which then dilfolves, and ads brifkly 
on the tin-foil. 
It is well known that the adion of the nitrous 
acid on tin is always accompanied with confider- 
able heat and effervefcence, and that the folution 
of metallic falts in watry liquors is haflened by 
heat. 
In our experiment, the warmth generated by 
the firft adion of the cupreous folution, promotes the 
deliquefcence of the cryffallized fait. The union 
of the acid with the tin is rapid, not only as being 
aflifted by heat, but on account of the great fur- 
face expofed ; whence the ftrong frothing, and 
the extraordinary heat, by which the redundant 
moifture is carried away, and the undecompofed 
part of the cupreous fait, together with that lately 
formed with the tin, perfedly dried. 
The heat generated upon both furfaces of a 
large expatife of tin, is concentrated by clofelv 
coiling it into a fmall compafs, and being retained 
by the various furrounding laminae of metal, it is 
neceflarily accumulated to a quantity, which, if 
we may judge from the touch, is more than fuf- 
ficient to fire the dry cupreous fait. 
The fait formed with tin, and the nitrous acid, 
burns and fparkles in a red heat. Catching fire, 
therefore, from the ignited cupreous fait, it burns 
T 2 with 
