1890-91.] Mr Irvine and Dr Gibson on Manganese Deposits. 59 
From the behaviour of manganese as above described, we have 
come to the conclusion that the formation of sulphide of manganese 
cannot be a result of the animal life, or the decomposition of animal 
matter at the sea-bottom, as supposed by Buchanan ; inasmuch as 
sea-water containing excess of carbonic acid must be always present. 
Buchanan does not give any evidence whatever to show that 
sulphide of manganese is formed, but appears to rely upon the 
supposed analogy in the behaviour of iron and manganese. Under 
conditions such as those referred to by him, sulphide of iron is 
necessarily formed. Unlike sulphide of manganese, sulphide of 
iron is readily formed in the presence of sea-water, whether mixed 
with carbonate of lime or not, and solutions of carbonic acid or 
bicarbonates do not decompose it or prevent its formation. 
Thus in all cases where, through the life processes of animals, 
sulphide of iron is formed as a result of the reduction of sulphates, 
the excess of carbonic acid necessarily formed at the same time 
must prevent the formation of sulphide of manganese. 
This holds equally in the case of the decomposition of the dead 
bodies of animals at the sea-bottom. 
On a Difference between the Diurnal Barometric Curves 
at Greenwich and at Kew, By Alexander Buchan, 
LL.D. 
(Read June 16, 1890.) 
In the “Challenger” Report on atmospherical circulation, the 
diurnal barometric curves at Gries and Klagenfurt in the Tyrol, and 
at Cordova in the Argentine Republic, are specially examined. 
The most noticeable feature of these daily barometric oscillations 
is their very large amounts, those at Gries, for example, though in 
lat. 46° 30' N., being quite tropical in amount ; and the singular 
circumstance is that in no season does the morning minimum fall so 
low as the daily mean. Gries, Klagenfurt, and Cordova are each 
situated in a deep valley. In such situations, during night, the 
whole surface of the region is cooled by radiation below the air 
above it, and the air in immediate contact with the ground becoming 
