188 W. M. HAMLET. 
building his famous London churches, clamped some of the 
stones together with iron clamps—a method which sounds 
both safe and simple, but in the course of years the iron 
had become so rusted and in the process of rusting had 
consequently so much expanded that the stones were 
loosened and burst asunder, so much so that only last year 
St. Bride’s church steeple had to be pulled down and a new 
one is now in process of construction. Iron rust is simply 
iron plus oxygen and moisture, so that the rust must neces- 
sarily occupy more space than the iron from which it was 
formed, the difference being about double. 
The chemical composition of rust is held to be that of 
the hydrated oxide of iron, the oxide represented by the 
formula Fe.O; plus one or two molecules of water. The 
best authorities agree in admitting the presence of two 
water molecules corresponding to a formula of F,0;(OH2), 
or Fe.0.,(OH);. The formation of rust is due to the action 
of oxygen and water on metallic iron, the action being 
greatly accelerated by the further action of carbonic acid 
gas, as these compounds are present everywhere both in 
the air and in water, it therefore comes to pass that iron 
will rust almost anywhere, but never without oxygen, even 
if immersed in water. I have some specimens of iron and 
steel which I hermetically sealed up in glass more than 
fifteen years ago, and I produce them to-night looking as 
bright and as clean as when I sealed them up, The water 
used was pure distilled water, all the oxygen being removed 
from it by prolonged boiling. I have before me some iron 
wire that has been packed in quicklime for about two 
years, and it is quite bright and clean, showing that if you 
exclude oxygen and carbon dioxide you may even, in the 
presence of water have no rust; or by excluding water and 
carbon dioxide even in the presence of oxygen no rusting 
occurs. 
