1833.) Chemical Analyses. 437 
ever could have been aimed at by its inventor ; that of gulling those who 
were foolish enough to put their trust in it. The following facts give 
_ authentic testimony of the worthlessness of the invention :— 
“The Renown, a new ship built at Port Glasgow, her first voyage to India, was- 
sheathed with this metal ; she had scarcely been at sea a month before the sheath- 
ing showed a rough and unclean appearance like a piece of wood which had 
been long in the water, but without the grass to it, and this kept going on worse 
and worse: and it was observed from the bowsprit, when the vessel pitched, that 
in many places it hung from the bottom like pieces of rags ; in some places large 
pieces were entirely gone, and what remained shewed every symptom as if it 
would soon follow, which it did: on examination of the pieces which came off, 
they appeared spotted, as if oxidizing fast into small holes ; by the time the ship 
arrived here many hundred sheets were gone from the bottom, and what was 
left as far as could be seen was very unclean.”’ 
The metal in fact is nothing but a soft pewter, consisting of 95 parts 
of lead, and five of tin mixed with some antimony. Its specific gravity 
of 11.130 corroborates this analysis. No trace of mercury could be dis- 
covered by heating it in a retort to a temperature at which this metal 
would have risen in distillation. 
The invention may have been suggested by an American pateut taken 
out in London in 1831 for a sheathing metal of zinc and copper, com- 
bined in the proportions of 95 zinc to 5 copper. This compound, 
although superior to the pewter on account of its stiffness, would 
probably be liable to corrosion much more rapidly than copper ; the 
inventor however states that the addition of a small portion of copper. 
greatly diminishes this liability, and adapts it well for the sheathing 
of ships and other purposes. 
Zinc by itself corrodes very rapidly in a damp climate. A remark- 
able instance of this was witnessed not long since, in removing some 
slabs of spelter which had been stored on the floor of a godown belong- 
ing to Messrs. CockEerett and Co, The lowermost slab was converted 
into a solid white substance throughout, apparently crystalline in its 
structure ; specific gravity 3.0. On heating in a test tube per se it 
disengaged much water and became yellow ; it dissolved with moderate 
effervescence in nitric acid. It was therefore a hydrated carbonate of 
zinc, or perhaps rather a mixture of hydrated oxide and carbonate, 
agreeing closely with the mineral from Bleyberg in Saxony, described 
by Smiruson* as hydrous carbonate, a sub-species of calamine, which 
he states to be a stalactitic formation. This is a remarkable instance 
of the formation of a natural insoluble mineral by artificial, though 
unintentional, means. 
* Txomson’s Chemistry, iv. p. 483. 
