119 
The above table shows bow very differently sea water acts 
upon divers brasses and the influence exercised upon the 
copper and the zinc composing them, by the existence in 
them of a very small proportion of another metal; thus, 
in pure brass the zinc is most rapidly dissolved (which, 
m passant , is the contrary to what takes place in galvanised 
iron), whilst it acts as a preservative to the copper. 
Tin, on the other hand, appears to preserve the zinc, but 
to assist the action of sea water upon the copper. 
The great difference between the action of sea water upon 
pure copper and upon Muntz metal seems to us to be due 
not only to the fact that copper is alloyed to zinc, hut to 
the small proportion of lead and iron which that alloy 
contains ; and there can he no doubt that shipbuilders derive 
great benefit by using it for the keel of their vessels. 
We were so surprised at the inaction of sea water upon 
lead that we were induced to compare its action with that of 
several distinct varieties of water, viz., Manchester Corpora- 
tion water — Avell water — distilled water in contact with air — 
the same deprived of air — and the following are the amounts 
of metals dissolved by 200 litres of these waters upon 1 square 
metre of surface during eight weeks. 
Grammes. 
Manchester Corporation Water 2094 
Well Water 1-477 
Distilled Water (with air) 110003 
,, ,, (without air) 1-829 
SeaWater 0038 
These figures require no comment, as they confirm our 
previous result that sea water has no action on lead. 
Mr. John Robinson exhibited specimens of iron and brass 
which had been acted upon by the water of the river Medlock, 
and stated he had found that an alloy of lead, tin, and 
antimony, resisted the action of sea water better than any 
other metal or alloy he had tried. 
