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 vicinity of Austin, Texas. This lies about twenty-five feet below the Austin Chalk, near Austin. A like layer occurs about 100 feet below the Austin Chalk in the Big Bend country. Here I have found the markings in localities thirty miles apart. They occur at the north point of Mariscal Mountain and in a number of places near the Fossil Knobs and on the Chisos Mining Company property at Terlingua. Unprofitable as observations on such a simple matter as this may seem, I find that other geologists have given it some attention. Quite recently, Dr. John M. Clarke[A] has figured slabs showing what has been described as _Fucoides graphica_, by Hall. The markings figured by Professor Clarke are undoubtedly of the same kind as those I have found in the Eagle Ford. They occur in the Upper Devonian in New York. I also find that the formation of ice crystals in wet mud has been observed in the clays about Boston by Marbut and Woodworth.[B] Other observations of similar recent markings are said to have been made by some English geologists.