. Bulletin of the Geological Society of America. Geology. 366 W. H. TWENHOFEL IMPRESSIONS BY BUBBLES AND RAIN-DROPS being less than a hemisphere. There are no appreciable raised rims, the surface of the mud being flat from the depressions outward. The edges of the depressions are sharply defined and regular. The surfaces of the pits are smooth to the eye, but are irregular in microscopic detail (fig- ure 5). In the writer's experiments, bubbles were formed by having a spray of water fall on an artificial upland, the falling waters making the bubbles, which then floated into a tank in which the
. Bulletin of the Geological Society of America. Geology. 366 W. H. TWENHOFEL IMPRESSIONS BY BUBBLES AND RAIN-DROPS being less than a hemisphere. There are no appreciable raised rims, the surface of the mud being flat from the depressions outward. The edges of the depressions are sharply defined and regular. The surfaces of the pits are smooth to the eye, but are irregular in microscopic detail (fig- ure 5). In the writer's experiments, bubbles were formed by having a spray of water fall on an artificial upland, the falling waters making the bubbles, which then floated into a tank in which the water was kept at a shallow. Figure 6.—Imptessions made hy floating Bubbles In the lower left-hand corner of the photograph are impressions made by exploding bubbles in very liquid mud. level over clay and fine sand. After many bubbles had become anchored the mud was permitted to dry. Wherever bubbles remained until the mud had settled to an extent sufficient not to flow, impressions remained. Bubbles were also formed by mixing water and mud in a pan, the agita- tion creating the bubbles, which were anchored by the suspended mud settling on them. It was found that impressions of this kind were formed whenever shallow muddy waters had bubbles formed in them. They must be formed in large numbers on every tidal mud fiat and on every river. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Geological Society of America. [New York : The Society]
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
