334 
THE VOYAGE OF H.M.S. CHALLENGER. 
consideration of the external form, internal structure, and distribution of the magnetic 
spherules which have just been described. This conclusion is further confirmed by the 
fact that these spherules do not present any analogies with terrestrial bodies which, up 
to the present time, have been found in sedimentary or igneous rocks, while, as stated 
above, they present striking analogies with meteoric bodies, known with certainty to have 
fallen from extra-terrestrial space. 
The question of cosmic dusts has been discussed by Nordenskjold,^ Daubr^e,^ 
Tissandier,® and Meunier,^ and these, together with other scientific men, have presented 
numerous facts in support of the cosmic origin of certain metallic particles or silicates 
collected as atmospheric precipitations. It has been urged, however, with great justice, 
against the extra-terrestrial origin of certain reputed cosmic dusts, that they are con- 
stituted, from a mineralogical point of view, of the same mineral species as those 
forming the rocks appearing at the surface in the neighbourhood of the regions from 
which the dusts were collected. 
With reference to the particles of magnetic iron very often met with in atmospheric 
precipitations, which have sometimes been considered of cosmic origin, it may be pointed 
out that these, in all probability, have been derived from some telluric source ; especially 
is this the case when they are of irregular form, without a black coating, unaccompanied 
by silicates of a spherical form, and associated with organic or inorganic products derived 
from our soils. It may also be pointed out that many of these so-called cosmic dusts 
differ widely from each other in their chemical and mineralogical composition, which in 
itself points to a terrestrial rather than an extra-terrestrial origin. 
Although native iron is extremely rare in terrestrial rocks, careful researches have 
shown that native iron, even cobaltiferous or nickeliferous, is present in terrestrial rocks, 
for instance, in the basaltic rocks of Ireland and Iceland.® In this particular case it may 
> The flust collected in Greenland in 1870 by Nordenskjold, and believed by him to be of cosmic origin (Kryokonit), 
has l)een examined by von Lasaulx {Min. u. petr. Mittheilungen von Tschermak., Bd. iii. p. 517, 1881), who came to the 
conclusion that the mineral particles in fpiestion were of telluric origin. The specimens collected by Nordenskjold in 
his second journey in 188.3 were examined by Wiilling (Neues Jahrb. fur Min., etc., Beilageband vii. p. 152, 1890). 
According to Wiilfing the greatest part of the dust is composed of terrestrial minerals and organic matter, but he 
found some rare magnetic spherules, ()•! to 0‘2 mm. in diameter, of an opaque or transparent substance, which is in 
some cases isotnipic, and in others birefrangent ; he refers them to chondres. Wiilfing did not find spherules with 
metallic nuclei in the dust he examined. 
* In a paper just jtublished, Daubri-e (Comptes Rdulm, tom. cxi. andexii., 1890-1891), alluding to the cosmic 
spherules of the deep-sea deposits, expresses the opinion that they may be of volcanic origin, having been formed and 
projected by the gaseous explosions. But, so far ns we know, such spherules as those described are not found in 
volcanic ashes. 
* O. Tissandier, Comptee Rendu*, tom. Ixxxi. p. 57G, 1875; tom. Ixxxiii. p. 76, 1876. 
* In their ].aicr: “ Presence de sj)h<5rules magnt-tiiiues analogues k ceux des poussieres atmospheriques, duns des 
roches npj«artiTiniit d’ancieiines [xiriodes gt'-nlogiques” {Compte* Rendu*, tom. Ixxxvi. p. 450, 1878), St. Meunier and 
Tiniandier descriW some magnetic sfiheniles dredged in deposits on the coasts of Tunis and Algeria and of Po.ssession 
Riy, or contained in strata of Cretaceous, Liassic, and Triassic age, also in rocks of the carboniferous or Devonian forma- 
tion. P>iit it ajq»cars from their description that all the sjiherules collected in these various conditions seem to be hollow 
spherules with a neck. ‘ See Andrews, Brit. Ass. Report for 1852, pp. .34-35. 
