Manganese Nodules in Loch Fyne 161 



grammes. Their volume was found to be 58 c.c., so that the 

 rage volume was 0-7 c.c., and the specific gravity 2-46. 

 Their form was roughly spherical, the largest, which was some- 

 what elongated, measured 13 x 9 x 6 millimetres, the average 

 diameter of them all being 11-4 millimetres. 



Of the eighty-three nodules so obtained I have split twenty- 

 tuo. When subjected to this treatment they are found to 

 differ in constitution from the majority of those obtained on 

 board the "Challenger." Although they had not been exposed 

 to any heat they were hard and sandy to the knife, and when 

 treated with strong hydrochloric acid, they left a large amount 

 iiural (chiefly quartz) sand. This difference, however, is 

 < -\ plained by the different kind of bottom from which they 

 were obtained. In dissolving up nodules which had come from 

 "red clay" in 2500 or 3000 fathoms, I always found the same 

 mineral sand left as on treating the clay in the same wav. 

 But the amount of sand was always quite insignificant as 

 compared with the clay; hence the nodules were easily cut 

 with tlu- knife. They, however, got harder on keeping. In 

 Loch Fyne the bulk of the mud consists of quartz sand, giving 

 the nodules the appearance of sandstone, whose binding 

 material is made up to a great extent of peroxide of manganese, 

 and hence the grim feeling to the edge of the knife. 



re a hard nucleus has been found it has always been a 

 piece of rock from the neighbouring shore, but in most instances 

 n out "t twenty-two examined) the ordinary arrange- 

 ment has been reversed, the nodule consisting of a soft rich 

 nucleus of peroxide of man^am-se. >urnunded by a black sandy 

 the whole env. l<.j>rd in tin- < i llv m.mnnillatrd 



black -kin. 



I hope very sh< be able to report more lull- 



; in tin- inc.intmir. I have only been able to iuir 



re by finding abundance of ;i \ide of manganese, 



'.\' recognisable quantities of cobalt, and the preseno 

 water. which, on being expelled by heat, has an alkaline 

 in empvnumatic odour, properties in which tlirv 

 agree with those which I had occasion to test on b< 

 dlenger." 



B. III. T I 



