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No. 113: Sep-Oct 1997

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Triangular Holes In Boulders

Recently, someone who wishes to remain anonymous, inspired after reading our Ancient Man, wrote us about a curious discovery of his. He had found some triangular holes in a granite boulder near Raleigh, NC. We have mentioned similar triangular holes before (SF#69/ 20), noting that hundreds of such holes had been recorded in boulders from Minnesota and the Dakotas to the eastern seaboard. We can now add to this dossier a photograph supplemented by this individual's testimony.

"Soon after Hurricane Fran struck Raleigh in September 1996, I was walking one of my customary routes along a local creek when my attention was arrested by a -ton granite boulder in the creek bed. The boulder had 3 holes drilled in its face, about 6 inches apart, and all in a straight line. (See photo.) I had not noticed this boulder before, so I'm fairly confident it was uncovered by the storm's 10-inch deluge of rain. Because the three holes seemed too close together to be blasting holes, I took a closer look at them and was surprised to see that they had "trianguloid" cross sections rather than round ones. By "trianguloid" I mean the cross section was thus:
Casts of the holes were made by using modeling clay. The expanded bases of the casts suggest that a shallow pit was pecked out of the granite before drilling began, and the constricted tips show that the first 3/4 inch of the drill bit was of a smaller diameter, perhaps to give it greater penetrating power so that the holes could be started more easily. The smaller "pilot" holes were also trianguloid in cross section."

(Anonymous; personal communication, May 27, 1997.)

Comment. In SF#69, it was proposed that the triangular holes were made in that shape so that wooden shafts, also of triangular cross section, could be inserted, given a quarter turn, thereby wedging the shaft firmly in place. This idea is behind the speculation that these strange boulders are really ancient "mooring stones." In truth no one really knows how old they are and what their purpose was. The final explanation may be mundane and/or trivial.

Reference. The Handbook Ancient Man, mentioned above, presents a wide spectrum of archeological anomalies. For a description, visit here.

'Trianguloid' holes drilled in granite "Trianguloid" holes drilled in a granite boulder as photographed from 10 feet. Scale length: 13 inches.

From Science Frontiers #113, SEP-OCT 1997. 1997-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987