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the amount of each metal dissolved by 100 litres of sea- 
water by acting upon one square metre of each metal : — 
Grammes. 
Steel 29-16 
Iron 27*37 
Copper (best selected) 12-96 
„ (rough cake) 13*85 
Zinc 5-66 
Galvanised Iron 1*12 
Block Tin 1*45 
Stream Tin 1*45 
Lead (virgin) Trace 
,, (common) Trace 
With regard to these experiments we notice that the method 
adopted for the determination of the amount of metal dis- 
solved was faulty — one by which small quantities could not 
be with certainty detected. This fact, although taking from 
the results some of their scientific value, does not deprive 
them of much practical interest. 
The colorimetric method, based upon the depth of colour 
produced with lead or copper on addition of ammonium 
sulphide, being capable of detecting exceedingly minute 
quantities of these metals in solution, was that adopted in 
the experiments about to be described, so that I am able to 
speak of the minute variations in the quantity of metal 
dissolved according to the length cf time during which it 
was exposed to the water, and the results of my experiments 
show that the action of sea- water upon lead and copper is 
exerted chiefly during the first few days of exposure, also — 
which appeared at first somewhat remarkable — that the 
quantity of metal in solution, after reaching its maximum, 
decreases when the metal is still exposed in the water. 
The method of procedure may be described as follows : — - 
Thin foil of lead and copper was used, cut into pieces two 
inches square, and thus exposing eight square inches of 
surface. In the instance of the copper-foil it was effectually 
