812 
THE VOYAGE OF H.M.S. CHALLENGER. 
in diameter ; they are never perfect spheres, as in the case of the black spherules with a 
metallic centre ; and sometimes a depression more or less marked is to be observed in 
the periphery. When examined by the microscope it is seen that the lamellae which 
compose them are applied the one against the other, and have a radial eccentric disposi- 
tion. It is the leafy radial (‘ radialblattrig ’) structure, like that of the chondres of 
bronzite, which predominates in the preparations. The granular structure of the chondres 
of olivine is observed much less rarely, and indeed there is some doubt about the indi- 
cations of thisl ast type of structure. Fig. 297 shows the characters and texture of one 
of these spherules magnified 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 it has been necessary to study them with reflected light, or to limit 
the observations to the study of the broken fragments. 
“These spherules break up along the lamellae, which are seen to be extremely fine 
enstatite. From 3500 fathoms Central represented in fig. 297, highly magnified. 
South Pacific. 
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 seen that they have one 
optic axis. It is observed also that when several of these lamellae are attached, they 
extinguish exactly at the same time, so that everything seems to indicate that they form 
a single individual. 
“ In studying these transparent and very thin fragments with the aid of a high 
magnifying power, it is observed that they are dotted with brown-black inclusions, dis- 
posed with a certain symmetry, and showing somewhat regular contours ; these inclusions 
are referred to magnetic iron, and their presence explains how these spherules of bronzite 
are extracted by the magnet. It is to be observed, however, that they are not so strongly 
magnetic as those with a metallic nucleus. 
“They are designated bronzite rather than enstatite, because of the somewhat deep 
tint which they present ; they are insoluble in hydrochloric acid. Owing to the small 
