608 Mr. J. Y. Buchanan on Chemical Work 



parative shallowness, the depth being in general under 2000 fathoms. 

 Whenever the dredge or trawl was used in that ocean it brought up 

 large quantities of stones ; but they were invariably fragments, more 

 or less rounded, of granitic and igneous rocks, and I did not notice 

 any manganese. On the 13th of March, however, when approaching 

 Australia, the depth increased to 2600 fathoms ; a very large haul of 

 manganese nodules was obtained, presenting the same general charac- 

 teristics as those in the Atlantic. In the Pacific the amount of man- 

 ganese found has been immense, there being hardly a sounding where it 

 could not be detected in small particles amongst the mud ; and, indeed, 

 in many parts the nodules occur in such quantity that the sounding-tube 

 has brought them up in considerable numbers at one time ; they have 

 also frequently come up sticking to the bottom of the water-bottle. 

 Here, however, they have chiefly come under the observation of my 

 colleague Mr. Murray, and will be treated of in his Eeport. Chemically 

 they are very much alike, as far as quantitative analysis can supply 

 information. They all contain one of the higher oxides of manganese in 

 preponderating amount, cobalt and nickel in notable quantity, and'copper 

 in traces, besides argillaceous and often sandy matter. I hope, when the 

 cruise is over, to be able, by means of quantitative analysis, to render a 

 detailed account of their nature, from which it may perhaps be possible 

 to obtain some hints as to their origin and development. 



Since the discovery of this most remarkable and unexpected occurrence 

 of a mineral, having much resemblance to psilomelane, evidently forming 

 at the bottom of the sea, I have taken every opportunity of examining 

 specimens of peroxide of manganese from terrestrial sources; and in 

 many cases I have found them to resemble the marine mineral in several 

 points, especially in nodular structure and in giving off alkaline water 

 when heated. Some peroxide of manganese which I got from the mines 

 near Paarl, about thirty miles from Cape Town, had most perfectly 

 nodular structure, but was extremely hard, whereas our nodules, when 

 freshly brought up, can generally, although not invariably, be easily cut 

 with a knife ; but they increase very markedly in hardness when exposed 

 to the air, even for only a few weeks. I do not attach very much im- 

 portance to the fact of its giving out alkaline water, for this is a pro- 

 perty which I have found to be very generally possessed by rocks and 

 minerals. Of the zeolites, for instance, which were found in Kerguelen, 

 there was not one which did not give out alkaline water with a very per- 

 ceptible empyreumatic smell when heated. 



It has been mentioned above that the dredge frequently brought up 

 large quantities of stones in the Antarctic Ocean. Amongst them were 

 almost invariably fragments of granite or syenite, as well as of both 

 basalt and trachyte. On the 2nd February, 1874, when between Ker- 

 guelen and Heard Islands, a very large quantity of stones was brought 

 up in the dredge from a depth of 150 fathoms. Amongst them were a 



