The first and most well-known result was from their first measurements—that the distance between two adjacent pendulums at the bottom was slightly larger than at the top (about 1 inch out of 15 feet). This was at a time when the fruits of the industrial revolution were just making it into people's homes and many people had a great interest in science and the promise it had for their future. Thus it is not too surprising that a detailed account these early results appeared in the local newspaper, the Daily Mining Gazette (Oct. 8, 1901). The reporter suggested that possibly some new phenomenon had been discovered. The results received national attention when the story was picked up by several other newspapers resulting in considerable speculation about the cause for this unexpected result. As one might expect, included were some rather unorthodox explanations. In fact, one can find these first results still cited even today (usually incompletely, incorrectly, and/or with significant creative embellishments) as evidence for a hollow Earth,* government conspiracies, coverups, UFOs, and/or for the general failure of Newton's law of gravity.

In the introduction of his 1902 article in The Engineering and Mining Journal,** where the full plumb bob experiments are reported, McNair provides a rather low-key response to the hoopla:

The publication ... in the Portage Lake Mining Gazette of the fact that a divergence in the plumb lines had been observed, attracted considerable attention, and brought forth many attempts to explain its existence. Those most familiar with the conditions had no satisfactory theory to offer. To them it was evident that more data must be secured before the cause could be correctly assigned.

McNair considered only two of the many explanations to be worth mention—a gravitational attraction to the walls of the shaft and magnetic effects. The gravitational effect was easily shown to be much too small. The group proceeded to use different materials for the weights and wire, as well as different positions, ventilation conditions, a pair of 4,440 foot pendulums in shaft #4, etc., for additional measurements.*** In some cases the pendulums were closer together at the bottom, though in most cases they were farther apart and there was no difference seen between the use of magnetic and non-magnetic materials. Based on a very strong correlation with ventilation conditions, they concluded that the effect was entirely due to the significant (natural) airflow in the mine shafts.

* When asked of the "hollow Earth" hypothesis in 1943, Fisher said the idea was "too absurd for serious scientific thought."

** Vol. 73, pages 578-580, (1902). A shorter version can be found in Science, Vol. XV, p. 994-6, (June 1902). Note that by this time, the Portage Lake Mining Gazette had changed its name to the Daily Mining Gazette, however McNair, as well as others, sometimes referred to it by its old name in this and several future references.

*** During winter of 2004/2005, these pendulums were recognized by Guinness World Records as having set the record for the World's Longest Pendulum. For information on other types of long period pendulums, look here.

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