28 PAPERS, ETC. 
weak voltaic battery, in constant action for three months, 
the apparatus being kept in a dark room. At the end of 
the above period I removed the bricks, and found that the 
negative end of the upper brick was rather strongly con- 
nected with the lower half brick on which it rested ; and on 
foreing them asunder I discovered that the cementing ma- 
terial was composed of cerystalline arragonite, some of 
which was formed upon both the united surfaces of the 
bricks, in snow-white needle crystals, radiating from their 
common centre; others were in the form of well-defined 
six-sided prisms, with flat terminations. These latter took 
shelter in some of the cavities of the bricks.. The ex- 
planation of this is simple enough. The bricks were made 
of clay containing a certain per centage of lime. The 
water into which they were plunged contained a certain 
proportion of hydrochloric acid as one of its component 
parts. This acid was directed to the positive end of the 
brick, where it acted on the lime at that end, forming 
muriate of lime, the acid of which was retained at the 
positive end, and the lime, attracting carbonie acid from 
the water, formed carbonate of lime, which was directed to 
the negative end of the brick, where it shot out in erystals 
of arragonite. Why arragonite was formed here, instead 
of common carbonate of lime, Iam at present quite at a 
loss to guess. I had the pleasure of shewing this formation 
to two highly scientific gentlemen, one of them a gifted 
foreigner, and one of the most distinguished chemists in 
Europe. I have at other times formed arragonite in dif- 
ferent modes, but never could account for the reason why 
arragonite appears at one time, and common carbonate of 
lime at another, either in art or nature. The present 
theory of cerystallization is most imperfect, little being 
known about it. I once by chance hit upon a mode of 
