He thinks that it may have been the origin of the Greek fret or meander pattern. Later still it was adopted even by the early Christians as a suitable variety of their cross, and became variously modified in form and was used as a charm. D'Alviella[47] expresses his doubts concerning the theory advanced by Greg[48] to the effect that the Swastika is to be interpreted as a symbol of the air or of the god who dwells in the air, operating sometimes to produce light, other times rain, then water, and so on, as is represented by the god Indra among the Hindus, Thor among the Germans and Scandinavians, Perkun among the Slavs, Zeus among the Pelasgi and Greeks, Jupiter Tonans, and Pluvius among the Latins. He disputes the theory that the association of the Swastika sign with various others on the same object proves its relationship with that object or sign. That it appears on vases or similar objects associated with what is evidently a solar disk is no evidence to him that the Swastika belongs to the sun, or when associated with the zigzags of lightning that it represents the god of lightning, nor the same with the god of heaven. The fact of its appearing either above or below any one of these is, in his opinion, of no importance and has no signification, either general or special. D'Alviella says[49] that the only example known to him of a Swastika upon a monument consecrated to Zeus or Jupiter is on a Celto-Roman altar, erected, according to all appearances, by the Daci during the time they were garrisoned at Ambloganna, in Britain. The altar bears the letters I. O. M., which have been thought to stand for Jupiter Optimus Maximus. The Swastika thereon is flanked by two disks or rouelles, with four rays, a sign which M. Gaidoz believes to have been a representative of the sun among the Gaulois.[50] Dr. Brinton[51] considers the Swastika as being related to the cross and not to the circle, and asserts that the Ta Ki or Triskeles, the Swastika and the Cross, were originally of the same signification, or at least closely allied in meaning. Waring,[52] after citing his authorities, sums up his opinion thus: We have given remarks of the various writers on this symbol, and it will be seen that, though they are more or less vague, uncertain, and confused in their description of it, still, with one exception, they all agree that it is a mystic symbol, peculiar to some deity or other, bearing a special signification, and generally believed to have some connection with one of the elements--water. Burton says:[53]