other; and on other rocks they would
be found crossing in close networks. In the summer of 1904 I again found
my ice markings on a layer of arenaceous limestone in the same formation
in the Big Bend country in Texas. This time I collected some specimens
which were subsequently photographed. One of these photographs is shown
in Plate II. Again in 1906 I noticed the same markings on some thin
sandy flags which occur in the Del Rio clay near the city of Del Rio. In
this case the needle-like crystals were somewhat more slender than those
previously seen, and some were slightly curved and somewhat more
elongated. These of course interested me as showing the occurrence of
freezing temperatures no doubt at a somewhat earlier time than that
pertaining to my previous observations.

During all these years my residence was in Illinois, and I was naturally
watching for similar markings in recent mud, resulting from late and
early frosts. I found them in the fall of 1909. At this time some
excavations were being made in the loess in Rock Island, when some rains
fell in the late fall. These rains evidently happened to give the mud
the amount of moisture necessary for such crystals to develop, as the
ground froze. The rains had washed the loess extensively, and I found a
number of places where it lay redistributed, with a fairly smooth
surface. It was evident that the moisture content of the ground,
together with the temperature conditions, determined the size and the
closeness of the frozen patterns. In places the crystals were long and
slender, in others they were short and stout. At some points they were
straight and in others slightly curved. Here and there the patterns were
close enough to resemble the fine lines which we sometimes notice in the
hoarfrost on windowpanes. In other places the crystals occurred in
radiating groups, and elsewhere they would form scattered separate
units. For preserving a record of what I saw, I poured plaster over
several patterns and had these casts photographed, as appears in Plates
VIII, IX, X. Placing these side by side with the photographs of the
patterns I have photographed from the Eagle Ford, it appears to me that
no doubt can be left as to the origin of the markings found in the
fossil state.

Recently I have found that these ice crystal marks are quite common at
one horizon in the Eagle Ford beds of Brewster County, in Texas. There
is also a layer in which they can be usually seen in the