MARCH, 1907. IRON METEORITES — FARRINGTON. 107 
all of the members of the classes conform in composition to the aver- 
age. Were all the groups equally well known, it is probable, too, that 
the gradation of percentage of Fe would be even more uniform than 
here shown. The medium octahedrites, for example, while numerous, 
have been as a whole imperfectly analyzed. Moreover, some of the 
meteorites classed as medium octahedrites, which are characterized 
by low percentage of iron, such as Algoma and Glorieta Mountain, 
have width of lamelle such as to place them near if not in the fine 
octahedrites. 
The apparent conclusion from the above results is, that the con- 
tent of nickel influences the structure. It may also account for the 
change from a hexahedral to an octahedral structure, since the irons 
with a hexahedral structure have the lowest per cent of nickel. So 
constant and definite does this relation hold, that given a certain struc- 
ture the per cent of nickel can probably be stated more accurately 
by this principle than it has been determined in some analyses. The 
per cent of nickel in iron meteorites as a whole, as shown by the re- 
liable analyses, lies between five and twenty-six per cent. An excep- 
tion to the latter figure may be found in the quoted analyses of Lime- 
stone Creek, but of this unfortunately no complete analysis exists. 
The somewhat doubtful Oktibbeha is also an exception, its percentage 
of nickel reaching sixty per cent. Cobaltin the iron meteorites rarely 
exceeds one per cent. No constant relation in amount appears to 
exist between it and nickel, although perhaps as a rule it is higher 
with higher nickel. Copper is doubtless, as claimed by Smith, a con- 
stant ingredient of iron meteorites. It is usually only a few hundredths 
of one per cent in amount, but may reach a few tenths. Chromium 
is shown by the analyses to be a frequent though not constant ingre- 
dient in minute quantities. In many cases it is probably present as 
daubreelite, but also, as suggested by Cohen, it may occur as an ele- 
ment alloyed with nickel-iron. _ Reports of the presence of manganese 
and tin are so frequent as to leave little doubt that they occur in many 
iron meteorites, perhaps alloyed as metals. The presence of platinum 
and iridium has been proved by Davison in Coahuila and Franceville, 
and doubtless could be found to exist in more meteorites if proper 
search were made. Gold was reported in Boogaldi by Liversidge, but 
in so small a quantity as to make its determination as yet not quite 
positive. The presence of occluded gases has been determined in but 
few cases. ‘The constant presence of phosphorus in iron meteorites 
is a feature shown by the analyses. Apparently no iron meteorite Is 
lacking in this element altogether, and in amount and constancy it con- 
