Feb. 15, 1877] 



NATURE 



341 



the bottom itself. Large pieces of this nature were taken several 

 times. 



The escape of carbonic acid through the floor of the ocean 

 near volcanic islands may in these regions greatly accelerate the 

 processes which end in the deposition of the peroxide of man- 

 ganese, and account for the great abundance of it in some such 

 localities where we found it. 



Native Iron and Cosmic Dust. 



While examining the deposits during the cruise I frequently 

 observed among the magnetic particles from our deep sea clays 

 small round black- coloured particles which were attracted by 

 the magnet, and I found it difficult to account for the origin of 

 these. 



On our return home I entered into a more careful examination 

 of the magnetic particles. By means of a magnet carefully 

 covered with paper I extracted thefe pa.iicles from the deposits, 

 from the pumice-stones, and from the manganese nodules of 

 many regions. The great majority of these magnetic particles 

 are magnetic iron ore and titaniferous iron, either in the form of 

 crystals or as fine dust. In the clays and in the manganese 

 nodules from stations far from land and in deep water there were 

 again noticed many small round spheres among the magnetic 

 particles. 



On mentioning this to Prof. Geikie he suggested that 1 should 

 try the method employed by Prof. Andrews, of Belfast, for de- 

 tecting minute particles of native iron. 



This process consists in moistening the magnetic particles, 

 which have been extracted by means of the magnet, with an 

 acid solution of sulphate of copper, when copper is at once 

 deposited on any native particles which may be present. In 

 this way I have detected native iron in many of our deposits, in 

 the powdered portions of manganese nodules, and in pumice- 

 stones. 



Prof. Andrews tells me that there can be little doubt that the 

 particles on which copper is deposited are native iron, as he has 

 found that it is not deposited oa nickel, and the chances of 

 cobalt being present are very slight. Prof. Andrews warned me 

 on the extreme precautions necessary in conducting these obser- 

 vations, that no iron from a hammer or other instrument should 

 get at the specimen under observation. 



It is true that all specimens of our deposits have been obtained 

 by means of dredges and iron gear, and some of these particles 

 may be from this source. 



Many of the particles must have another origin. I have taken 

 two of our manganese nodules, and washing them carefully, 

 taking care to let no iron instrument come near them, have 

 broken them by rapping them together. Then taking only the 

 interior parts of these nodules I have pulverised them in a porce- 

 lain mortar. The magnetic particles were afterwards extracted 



by a magnet covered with paper. Now, placing these particles 

 on a glass slide under the microscope, and adding the sulphate 

 of copper solution, there was in a few moments a deposit of 

 copper on several small perfect spherules, varying in size from 

 the luVir to the 35^ of an inch in diamtter. I have placed some 

 of these spherules under the microscope and now show them to 

 the Society. It will be noticed that on one the copper is not 

 deposited all over the sphere, but in ramified spider-like lines. 

 On the cut surface of a meteorite, from Prof. Sir Wyville Thom- 

 son's collection, which I also exhibit, the copper is precipitate<l 

 in precisely the same manner as on the little sphere on the man- 

 ganese nodule. Besides the spherules on which the copper is 

 deposited, there are others generally of a larger size and dark 

 colour. These are, so far as microscopic examination shows, 

 quite like the particles on the mammilated outer surface of this 

 Cape meteorite, also from Sir Wyville's collection. 



These spherules have hitherto only been noticed in those 

 deposits in deep water far from land, and where for many reasons 

 we believe the rate of formation of deposits to be very slow. 



They occur also only in those manganese nodules which come 

 from the same deep sea clays or deposits far from land. 



The particles of native iron found in pumice-stones are not 

 numerous, and never take the form of spheniles so far as ob- 

 served. Some of these particles of native iron may then come 

 from the dredge. Other particles come from the pumice and 

 the volcanic materials. Prof. Andrews long since showed that 

 minute particles of native iron existed in basalt and other rocks. 

 And lastly, the spherules of which I have been speaking, appear 

 to have a cosmic origin. 



The reason, for these spherules occurring only in deposits far 

 from land and in deep water, may be more apparent by refer- 

 ence to the ainiexed diagram, which might represent a section 

 from the west coast of South America out into the Pacific 500 

 miles. Along the shores of the continent, as at «, we have an 

 accumulation of river and coast detritus. At b in depths from 

 1,400 to 2,200 fathoms we have a globigerina ooze mostly made 

 up of surface shells. At c, in a depth of 2,300 to 3,000 fathoms, 

 all the surface shells are removed from the bottom. No coast 

 detritus reaches this area, and we find in the deposit pumice 

 stones, some volcanic ashes, manganese nodules, sharks' teeth, 

 and ear-bones of whales. It is only in areas like this that we 

 find sharks' teeth and ear-bones of cetaceans in any numbers. 

 Some of them from the same haul are deeply surrounded with 

 manganese deposit, and contain little animal matter, while others 

 have no deposit on them, and seem quite recent. These, and 

 other facts which might be mentioned, all argue for an exceed- 

 ingly slow rate of deposition. Now it is in these same areas that 

 the spherules of native iron and other magnetic spherules are 

 found, both in the deposits and in the manganese nodules from 

 them. 



*''<^.: 



'-'•'•^v 



sea level 



Finding them in this situation favours the iaea that they are of 

 cosmic origin, for in such places they are least likely to be 

 covered up or washed away. It is certainly difficult to under- 

 stand why the spherules on which tte copper is ]n-tcipated have 

 not become oxidised. If nickel be present in them, this may 

 retard oxidation to tome extent. 



The manganese depositions in our ocean deposits are very 

 different in structure and composition from any of the ores of 

 manganese I have had an opportunity of examining, and the 

 deposits of the deep sea far from land have not, so far as I know, 

 any equivalents in the geological series of rocks. 



All the subjects treated of in this paper are still under investi- 

 gation, and at some future time I hope to present a much more 

 detailed account. 



These obseivations seem to me to give ground for the follow- 

 ing conclusions : — 



First. — That volcanic debris, either in the form of pumice 

 stones, ashes, or ejected fragments, are universally distributed in 

 ocean deposits. 



Second. — That pumice stones are continually being carried 



into the sea by rivers and rains, and are constantly floating on 

 the surface of the ocean far from land. 



Third. — That the clayey matter in deposits far from land is 

 principally derived from the decomposition of the feldspar in 

 fragmental volcanic rocks, though in the trade wind region of the 

 North Atlantic the dust of the Sahara contributes much material 

 for clay. 



Fourth. — That the red earth of Bermuda, Bahamas, Jamaica, 

 and other limestone countries, is most probably originally derived 

 from the decomposition of pumice stone, while these limestones 

 were in the process of formation. 



Fifth. — That the peroxide of manganese is probably a secon- 

 dary product of the decomposition of the volcanic rocks and 

 minerals present in the areas where the nodules of manganese 

 are found. 



Sixth. — That there are many minute particles of native iron 

 in deposits far from land ; that some of these particles are little 

 spherules ; that these last, as well as some other spherules which 

 are magnetic, have probably a cosmic origin. 



Seventh. — That the peroxide of manganese depositions in the 



