THE MEXICAN METEORITES. 
49 
The relative occurrence of iron and stony meteorites is of 
such a notable character that it deserves some consideration, 
especially in connection with the meteorites of Mexico. The 
iron meteorites contain no constituents which are not found 
under other conditions in the earth’s crust; but, while the 
peculiar combinations of iron, nickel, and other elements 
placed these bodies in a special class, they did not furnish 
sufficient evidence in themselves of an extra-terrestrial origin. 
This evidence was discovered, however, in a very conclu¬ 
sive manner when iron meteorites were seen to fall in the 
same manner as stony ones had been observed. These iron 
bodies, whose fall had been witnessed by many trustworthy 
people, were found to contain the same constituents com¬ 
bined in the same proportions as those similar bodies that 
had been discovered on the earth’s surface. The iron and 
nickel masses occupy one extremity of the meteoric scale and 
the so-called stony bodies the other. From the astronomical 
standpoint it is exceedingly difficult to draw the line that 
separates the two classes. It is almost, if not quite, impossi¬ 
ble to find a stony meteorite of any considerable size that 
contains no trace of iron. From specimens containing grains 
of iron only visible with a microscope there is an uninter¬ 
rupted gradation to those containing nodules ranging in 
diameter from a millimeter to a centimeter. When a stony 
meteorite falls to the earth it generally breaks into many 
fragments either just before or at the time of its collision 
with the earth’s surface, and in most cases the ruptured sur¬ 
faces plainly indicate the nature of the catastrophe. 
I know of no case where an iron meteorite shows any indi¬ 
cation of having been broken, twisted, or torn off from another 
mass of the same material. If the mass is known to have 
traversed a long path in the earth’s atmosphere it will be 
found with one surface, presumably that of the preceding 
end or side, exhibiting a modified form, in some instances 
showing the effect of heat of sufficient intensity to partially 
fuse the outside of the mass, but there is no evidence of rup¬ 
ture by tearing away from another body. For many years 
