590 



NATURE 



[Aprtl 17, 1884 



particles of native iron, in their transit tlirougli the air, must 

 undergo combustion, and, like small portions of iron from a 

 smith's anvil, be transformed either entirely or at the surface 

 only into magnetic oxide, and in this latter case the nucleus is 

 protected from further oxidation by the coating which thus 

 covers it. 



One may suppose that meteorites in their passage through the 

 atmosphere break into numerous fragments, that incandescent 

 particles of iron are thrown off all round tliem, and that these 

 eventually fall to the surface of the globe as almost impalpable 

 dust, in the form of magnetic oxide of iron more or less com- 

 pletely fused. The luminous trains of falling stars are probably 

 due to the combustion of these innumerable particles, resembling 



Fig. 2.— Bl.ick spherule with metallic nucleus (60 : i). This spherule, 

 covered with a coaling of black shining magnetite, represents the mast 

 frequent shape. The depression here shown is often found at the surface 

 of these spherules. From 2375 fathoms South Pacific. 



Fig. 3.— Black spherule with metallic nucleus (60 : i). The black external 

 coating of magnetic oxide has been broken away to show the mel.-)llic 

 centre, represented by the clear part at the centre. From 3150 fathoms 

 Atlantic. 



the sparks which fly from a ribbon of iron burnt in oxygen, or 

 the particles of the same metal thrown off when striking a flint. 

 It is easy to show that these particles in burning take a spherical 

 form, and are surrounded by a layer of black magnetic oxide. 



Among the magnetic grains found in the same conditions as 

 these we have just described are other spherules, which we refer 

 to the chondrcs, so that if the interpretation of a cosmic origin 

 for the magnetic spherules with a metallic centre was not esta- 

 blished in a manner absolutely beyond question, it almost be- 

 comes so when we take into account their association with the 

 silicate spherules, of which we have now to speak. It will be 

 seen by the microscopic details that these spherules have quite 

 the constitution and structure o{ chondres so frequent in meteor- 

 ites of the most ordinary type, and on the other hand they liave 

 never been found, as far as we know, in rocks of a terrestrial 

 origin ; in short, the presence of tliese spherules in the deep-sea 

 deposits, and their association with the metallic spherules, is a 

 matter of prime importance. Let us see how we distinguish 

 these silicate spherules, and the points upon which we rely in 

 attributing to them a cosmic origin. 



Among the fragments attracted by the magnet in deep-sea 

 deposits we distinguish granules slightly larger than the spherules 

 with the shining black coating above described. These are 

 yellowish-brown, with a bronze-like lustre, and under the micro- 

 scope it is noticed that the surface, instead of being quite 

 smooth, is grooved by thin lamell:E. In size they never exceed 

 a millimetre, generally they are about O'J mm. in diameter ; they 

 are never perfect spheres, as in the case of the black spherules 

 with, a rttetallic centre ; and sometimes a depression more or less 

 marked is to be observed in the periphery. When examined by 

 the microscope we observe that tlie lamella; which compose thcin 

 are ajiplied the one against the other, and have a radial eccentric 

 disposition. It is the leafy radial structure (radialbldttrig), like 

 that of the chondres of bronzite, which predominates in our 

 preparations. We have observed much less rarely the serial 

 structure of the chondres with olivine, and indeed there is some 

 doubt about the indications of this last type of structure. Fig. 4 

 shows the characters and texture of one of these spherules magni- 

 fied 25 diameters. On account of their small dimensions, as 

 well as of their friability due to their lamellar structure, it is 

 difficult to polish one of these spherules, and we have been 

 obliged to study them with reflected light, or to limit our 

 observations to the study of the broken fragments. 



These spherules break up following the lamella, which latter 

 are seen to be extremely fine and perfectly transparent. In 

 rotating between crossed nicols they have the extinctions of the 



rhombic system, and in making use of the condenser it is scci: 

 that they have one optic axis. It is observed also that whc, 

 several of these lamellar are attached, they extinguish exactly ni 

 the same time, so that everything induces us to believe that the\ 

 form a single individual. 



In studying these transparent and very thin fragments with thi 

 aid of a high magnifying power, it is observed that they an- 

 dotted with brown-black inclusions, disposed witli a certain 

 symmetry, and showing somewhat regular contours ; we refet 

 these inclusions to magnetic iron, and their presence explains 

 how these spherules of bronzite are extracted by the magnet. 

 We would observe, however, that they are not so strongly 

 magnetic as those with a metallic nucleus. 



We designate them under tlie name of bronzite rather than t>\ 

 enstatite, because of the somewhat deep tint which they present ; 

 they are insoluble in hydrochloric acid. Owing to the small 

 quantity of substance at our disposal, we were obliged to limit 

 ourselves to a qualitative analysis. We have found -in them 

 silica, magnesia, and iron. 



We have limited our remarks at this time to these succinct 

 details, but we believe tliat we liave said enough to show that these 

 s|iherules in their essential characters are related to the chondres 

 of meteorites, and have the same mode of formation. In con- 

 clusion, we may state that when the coating, of manganese 

 depositions, which surround sharks' teeth, ear-bones of Cetaceans 

 and other nuclei, is broken off and pounded in a mortar to 



F'g. 4— Spherule of bronzite (25 : i) from 3500 fathoms in the Central South 

 Pacific, showing many of the peculiarities belonging to chondres ot 

 bronzite or enstatite. 



fine dust, and the magnetic particles then extracted by means of 

 a magnet, we find these latter to be composed of silicate spherules, 

 spherules with a metallic centre, and magnetic iron, in all 

 respects similar to those found in the deposits in which the 

 nodules were embedded. 



We have recently examined the dust collected by melting the 

 snow at the Observatory on Ben Nevis, in order to see whether, 

 in that elevated and isolated region, we should be able to find 

 volcanic ashes or cosmic sphendes analogous to those -we have 

 described. This atmospheric dust, which we have examined 

 microscopically, has not shown any particles which could with 

 certainty be regarded as identical with those substances whicli 

 are the subject of this paper. Particles of coal, fiagments of 

 ashes, and grains of quartz predominated. Besides these, there 

 were fragments of calcite, augite, mica, and grains of rock of all 

 forms and of variable dimensions. These were associated with 

 fibres of cotton, of vegetables, splinters of limonite and of tin — 

 in short, everything indicating a terrestrial origin. 



In order to give an idea of the facility with which the winds 

 may carry these matters even to the summit of the mountain, we 

 may add that Mr. Omond has sent to us fragments of crystalline 

 rocks, some having a diameter of two centimetres, which, he 

 states, were collected on the surface of the snow at the summit 

 after the storm of January 26, 1884. 



Arrangements are being made to collect the dust at the top of 

 Ben Nevis during calms with great care. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE 

 College of Agriculture, Downton, S.^lisbury. — .At 

 the close of the winter session on Wednesd,iy, i6th inst., the 



