194 W. M. HAMLET. 
service we found no such blistering as that spoken of at 
Whitehaven.”’ 
By what means then can we secure the preservation or 
protection of iron against the inroads of the oxygen, water 
and carbon oxide molecules? The answer is that there are 
two fundamental principles on which a policy of protection 
can be based. Hither to alloy with the iron some resistant 
elements, or coat the metal with something that is un- 
affected by the corroding elements. By the introduction 
of such elements as silicon, carbon and phosphorus the 
iron is made much more resistant or rust and corrosion by 
acids generally, but the iron is then of the variety known 
as ‘cast iron,’ and cast iron is precluded where toughness 
and tenacity is demanded, so that we are thrown back on 
some such coating as an oil, a varnish, a paint or the film of 
the magnetic oxide when the Barfi-Bower process is used. 
A paint is a substance, usually a coloured earth or 
artificial chemical product, called a pigment, ground in 
some suitable medium such as oil, water, etc., by which it 
can be spread on the surface to be painted. It is therefore 
a very simple substance consisting of pigment and vehicle: 
the one should be for the preservation and decoration of 
an object, the latter should be transparent, free from 
colour, and ought to dry readily. The best paints or pig- 
ments I know of, for the protection of ironwork are :—a 
varnish having carbon as its pigment in asphaltum, red 
lead, iron oxide, and the many varieties of carbon. Un- 
doubtedly the best of media or vehicles is linseed oil which 
on exposure to the air becomes rancid with absorption of 
oxygen; this when spread over a surface in a thin layer 
dries to a tough skin which is insoluble in most liquids and 
even in ether, the union of the oil with the oxygen of the 
air forms a definite chemical oxidation product to which 
its repute and success is alone due. Turpentine is not to 
