On 16th December 1895 a paper written by Professor W. N. Hartley, F.R.S., Royal College of Science, Dublin, was read before this Society “On the Cause and Nature of Chemical Changes occurring in Oceanic Deposits,” in which he criticised and took exception to certain conclusions we had arrived at, which formed the basis of a paper read by us in March 1892, and published in the Transactions of the Society, Vol. xxxvii., Part ii., No. 23, under the title “On the Chemical Changes which take place in the Composition of Sea-water associated with Blue Muds on the Floor of the Ocean.”

At the time of writing his paper Professor Hartley had not seen ours, and was only in possession of the necessarily curtailed notice of it which appeared in Nature of January 24, 1895, from which he appears to have drawn inferences that a fuller knowledge would have altered. Practically, with the exception of one or two of our experimental results, Professor Hartley is in accord with us so far as the principal results are concerned. In taking exception to the formulæ by which we endeavour to explain the decomposition of sulphates in sea-water in the presence of organic matter and ferric-hydrate, or ferruginous clay, he assumes the equations we use to mean the same as that which would occur in a black ash furnace under the influence of great heat. Our object in adopting the explanation of the reaction which appeared in our paper was to render it as simple as possible; and occurring as it does in mud saturated with water, we did not think it necessary to specially refer to the hydrous condition of the salts.