117 
of the water, and suspended by flax rope attached to a 
wooden structure, to prevent any galvanic action taking 
place between the plates and the structure to which they 
were attached. 
The following are the amounts of metals dissolved : — • 
Grammes. 
Steel 105-31 
Iron 99-30 
Copper (best selected) 29-72 
Zinc 34-34: 
Galvanised Iron 14-42 
Lead (virgin) 25-69 
„ (common) 25-85 
The above figures suggest the following remarks : — • 
That the action has been much more intense, in this 
instance, than when the metals were placed in a limited 
amount of water at the laboratory. These results are due 
probably to several causes acting at the same time, viz. : — 
that the metal was exposed to the constantly renewing sur- 
face of an active agent ; and that there was also a considerable 
friction exerted on the surface of the plate by the constant 
motion of the water, there being at Fleetwood a powerful 
tide and rough seas. What substantiates this opinion is, 
that the lead plates undoubtedly lost the greater part of the 
weight, not by the solvent action of the sea water, but from 
particles of lead detached from them, in consequence of their 
coming in contact with sand and the wooden supports to 
which they were attached ; but this cause of destruction 
"having been observed with lead plates, it was afterwards 
carefully guarded against in the case of all the other metal 
plates. 
We also deemed it desirable to examine the action of sea 
water on various brasses. We therefore immersed for one 
inonth, plates of various alloys in that fluid, and proceeded to 
record our results : — 
