reinforcement, which rusted and disappeared, with the result
that in less than four years holes were made right through the
concrete. The sides, which were formed of slabs allowed to
harden before being placed in the structure, were unaffected
except for a slight roughening of the surface after being
exposed alternately to the sea and air for a period, of
thirteen years. Professor Moller referred also to several cases
which had come under his notice where cement mortar or concrete
became soft and showed white efflorescence when it had been
brought into contact with sea-water shortly after being made.

In experiments in Atlantic City samples of dry cement in powder
form were put with sea-water in a vessel which was rapidly
rotated for a short time, after which the cement and the sea-
water were analysed, and it was found that the sea-water had
taken up the lime from the cement, and the cement had absorbed
the magnesia salts from the sea-water.

Some tests were carried out in 1908-9 at the Navy Yard,
Charlestown, Mass., by the Aberthaw Construction Company of
Boston, in conjunction with the Navy Department. The cement
concrete was placed so that the lower portions of the surfaces
of the specimens were always below water, the upper portions
were always exposed to the air, and the middle portions were
alternately exposed to each. Although the specimens were
exposed to several months of winter frost as well as to the
heat of the summer, no change was visible in any part of the
concrete at the end of six months.

Mons. R. Feret, Chief of the Laboratory of Bridges and Roads,