38 Proceedings of Royal Society of Edinburgh. [sess. 
ponticum ” by the Franklands in their book on “ Micro-Organisms 
in Water” published in 1894, at page 458. It is not impossible 
that these organisms can live in such extraordinary conditions as 
described. However, the authors (Zelinsky and others) do not 
inform us whether the organisms were living or dead when found 
in the Black Sea mud. If living, this would prove the fact 
claimed for it, that this bacterium is able to live under such 
circumstances ; but if dead, it simply represents an organism which 
had been poisoned by its own effete products, and whose remains 
have sunk to the bottom and accumulated with the other organic 
remains there. In our paper we refer to this condition of the 
Black Sea, first brought into notice by Andrussow and others, but 
we accounted for the presence of sulphuretted hydrogen in such 
an amount there owing to the sea being practically land-locked, 
having no oceanic circulation, and where the amount of iron 
present in the suspended mud brought down by rivers was not 
sufficient to absorb or combine with the sulphur of the deoxidised 
sulphates, and so form a blue or black mud such as is deposited on 
ocean floors where ferruginous clays are abundant. The ferric oxide 
in these muds is readily blackened by sulphuretted hydrogen. 
Professor Hartley takes exception to the statement we made, 
that when sulphuretted hydrogen in solution in pure water is left 
exposed to air for a sufficient length of time, part of the sulphur 
combined with hydrogen as sulphuretted hydrogen, is oxidised into 
sulphuric acid. Our experiments were made with such care that 
we cannot accept as conclusive the argument produced to the 
contrary. As we performed our experiments, it was immaterial to 
us whether the sulphuretted hydrogen was decomposed or oxidised 
with the deposition of sulphur or not ; if so, the sulphur being in 
a fine state of division, in presence of water may have oxidised into 
sulphuric acid. The point that we wished to bring prominently 
forward was, that when a solution of sulphuretted hydrogen is 
exposed to the influence of air or oxygen, changes take place which, 
in the end, produce sulphuric acid. As we have shown from our 
experiments, sulphuretted hydrogen, when in excess, decomposes 
calcium and magnesium carbonates, both always present in blue 
muds, producing sulphides of these metals ; and it is beyond 
question that the sulphides so formed are, in their turn, decomposed 
