Hidromancy is the divination by water that was stated by Natalius Comes (d. 1852) as being initiated by the ancient sea god Nereus, but presently the term covers a variety of divinations ranging from crystalomancy to radiesthesia.
The Jesuit M. A. Del Rio (1551-1608) described several methods oif hydromancy. The first method described depicts a ring hanging by a string that is dipped into a vessel of water which was shaken. A judgment or prediction is made by the number of times which the ring strikes the sides of the vessel.
A second method is when three pebbles are thrown into standing water and observations are made from the circles formed when the objects strike the water.
The third method described depended upon the agitation of the water, this custom was prevalent among Oriental Christians of annually baptizing that element, at the same time as taking especial care to show that the betrothment of the Adriatic by the Doge of Venice had a wholly different origin.
A fourth method used colors of the water and figures appearing in it by which Varro stated that many prognostications were made concerning the Mithridatic War. This branch of the divination proved so important that it was given a separate name and there arose from it the divination of fountains whose waters were frequently visited. Among the most famous were the fountains of Palicorus in Sicily which destroyed many a criminal who testified falsely before them. A full description as to their usage and virtue was give by the Roman philosopher Microbus (c. 345-423 AD).
Pausanius (2nd century AD) described the fountain near Epidaurus dedicated to Ino into which loaves were thrown by worshippers hoping to receive an oracle from the goddess. If the loaves were accepted they sank in the water which meant good fortune, but if they were washed up from the fountain it meant bad luck.
Other divining spring stories were collected by the antiquary J. J. Bossiard to which Del Rio gave their origination. A custom of ancient Germans was to throw newborn children into the Rhine. It was thought if the child was spurious he would drown, but if he was legitimate he would swim. Such a custom appears to be a precursor of the 17th century custom of «swimming witches» perhaps related to the Anglo-Saxon law of trail by water established by King Athelstain.
In a fifth method of hydromancy mysterious words are pronounced over a glass of water, then observations are made of it spontaneous ebullience.
In the sixth method a drop of oil was let drop into a vessel of water, this furnished a mirror through which wondrous things became visible. This, Del Rio said, is the Modus Fessanus.
The seventh method of hydromancy was cited by Clemens Alexandrinus who cited that women of Germany watched the whirls and courses of rivers for prognostic interpretations. The identical fact was mentioned by J. L. Vives in his Commentary upon St. Augustine.
Also, in modern Italy, continued the learned Jesuit, there are still diviners who take three name of suspected thieves and write them on three little balls which they throw into water, he added, some were so profaned as to use holy water in this unsanctified practice.
In a fragment of M. T. Varro’s de Cultu Deorum the practice of hydromancy was attributed to Numa. A.G.H.