Friday, April 23, 2010

Net Sinker Cache

In 1992 the chance discovery of an artifact cache consisting of 80 pebble net sinkers was made by Les Kunkle, one of the museum’s active “Fort Hunter Dig” volunteers (Figure 1). Although the location, which is upriver from Harrisburg, yielded many prehistoric stone artifacts, the Late Archaic and Transitional periods seem to dominate, a finding that is not unusual for the lower section of the Susquehanna beyond Blue Mountain. Broadspears made from South Mountain metarhyolite of the Lehigh/Koens-Crispin type are common to the site as are the long and narrow stemmed bifaces of the slightly earlier Piedmont Archaic Period. Carved steatite kettle fragments and broken bannerstones which are also good time markers of the broadspear tradition are also present. It is important to point out that the net sinker cache was located in the “broadspear area of the site” suggesting that the association between the two artifact classes is likely more than sheer coincidence.

Fig. 1) Les Kunkle

Two lines of evidence suggest that this cache represents elements of a single net or a group of similar sized fishing nets—1) the context where they were found and 2) the general uniformity of individual net sinker’s size, shape and weight. Mr. Kunkle stated that “….the cache lay within a pocket of dark grayish soil about a foot in diameter that appeared pasty and organic….”. The dark soil matrix encapsulating the cache might indicate that the net sinkers were buried still attached to a casting net or other fishing device that subsequently rotted away over time.

Fig. 2) Net Sinker Cache

As seen above, each net sinker was bi-notched using a simple percussion method and shows little additional modification. There are no unusual differences noted in the types of lithic materials selected for these fishing components. The pebbles are of sedimentary origin comprised of medium coarse to fine grained sandstones and fine grained siltstones, brown, gray and purple in color, and river tumbled to form rounded to sub-rounded shapes. One is a fine grained platy shalestone which is a rock common to the valley’s water gaps. Sinker dimensions display a relatively tight range of measurements by category, seen particularly in the maximum thickness and maximum notch width data summarized in the table below. There is slightly more variability between net sinker length measurements which probably correlates to the increased variability in sinker weight and varying density of pebble lithic materials, although the data is not recorded in a way to make this comparison at present. This aside, the low range of variation between net sinkers to some extent illustrates the care taken to gather uniform sized pebbles from the river shoals.

Figure 3

The figure below presents the length/width/thickness measurements in millimeters of the pebble sinker cache (N=80). A rather consistent pattern is noted in the width at notch measurements taken at the narrowest point of each sinker. Statistically speaking, notch width measurements show a range of only 5.9 mm at one standard deviation and just over a centimeter within the 2-Sigma range. This means that roughly 68% of the net sinkers in this cache have a notch width ranging between 36.4-24.6 mm (~3.5-2.5 cm) and about 95% of the net sinkers in this cache have a notch width ranging between 42-19 mm (4.2-1.9 cm), with an average width of 30.5 mm (~3 cm).

Could this tight range of notch widths correlate to the spacing distance between knots in the fishing net to which they were attached ? If so, this would suggest that the ropes of the net were spaced about 3 cm2 apart or at roughly 1.25 square inch intervals—a net that would most likely be used to catch large fish.

Fig. 4

Total weight of the cache is 2,715.3 grams - a dead weight of pebbles that after notched and attached to a net, might be more useful for bottom dragging (i.e. capturing foods such as mussels, eels, crayfish or other bottom feeding critters.

We thank Mr. Kunkle for donating the net sinker cache to the State Museum of Pennsylvania where it is now curated and openly available for future study.

For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .

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