Ill 
4th. The effect of sulphuric acid was almost the same as 
that of hydrochloric, except that its surface action, particu- 
larly in the case of mild steel, was not so marked. 
It thus appears that the fibrous nature of the charcoal iron 
allows the acid and absorbed hydrogen to pass up through 
the interior of the mass for some 17 c.m. above the surface . 
of the acid, thus decreasing its toughness. The closeness of 
the grain of the steel and absence of fibre appear on the 
other hand to prevent this action. This difference in 
the behaviour of steel and iron is the more remarkable as 
the decrease of toughness consequent on immersion in acid 
is much greater with steel than with iron. 
Further, it is well worthy of notice that nitric acid, which 
does not evolve hydrogen on contact with iron, does not 
appear to perceptibly diminish the toughness of iron or steel 
immersed in it, nor do bubbles arise from the moistened 
fracture of these metals after immersion in it, as they do 
with acids which give off hydrogen by their action on iron. 
In view of the constantly increasing consumption of mild 
steel, and the proposal to introduce it in place of iron for 
ship building, the greater corrosive action of acids on mild 
steel than on iron has considerable interest. For it would 
seem to indicate that mild steel will more rapidly corrode 
than iron, and possibly this may render its use in shipbuild- 
ing to be attended with greater risk. 
Mr. R D. Darbishire, F.G.S., gave an interesting account 
of Dr. Schliemann’s Excavations and Discoveries on the 
Site of Troy, and exhibited some selected Photographs from 
his collections. 
“Results of certain Magnetic Observations made at 
Manchester during the year 1873,” by Professor Balfour 
Stewart, LL.D., F.R.S. 
These observations were made in a small wooden house, 
