chemical Agencies of Electricity . g 
times greater, but no traces of muriatic acid. There was 
much probability that the agate might contain some minute 
portion of saline matter, not easily detected by chemical 
analysis, either in combination, or intimate adhesion in its 
pores. To determine this, I repeated the experiment a second, 
a third, and a fourth time. In the second experiment turbid- 
ness was still produced by solution of nitrate of silver in the 
tube containing the acid, but it was less distinct ; in the third 
process it was barely perceptible : and in the fourth the two 
fluids remained perfectly clear after the mixture. The quan- 
tity of alkaline matter diminished in every operation ; and in 
the last process, though the battery had been kept in great 
activity for three days, the fluid possessed in a very slight 
degree only the power of acting on paper tinged with tur- 
meric ; but its alkaline property was very sensible to litmus 
paper slightly reddened, which is a much more delicate test : 
and after evaporation and the process by carbonate of am- 
monia, a barely perceptible quantity of fixed alkali was still 
left. The acid matter in the other tube was abundant ; its 
taste was sour ; it smelt like water over which large quan- 
tities of nitrous gas have been long kept ; it did not affect 
solution of muriate of barytes ; and a drop of it placed upon 
a polished plate of silver left after evaporation a black stain, 
precisely similar to that produced by extremely diluted nitrous- 
acid. 
After these results, I could no longer doubt that some 
saline matter existing in the agate tubes had been the source 
of the acid matter capable of precipitating nitrate of silver, 
and of much of the alkali. Four additional repetitions of the 
process, however, convinced me that there was likewise some 
other cause for the presence of this last substance ; for it 
