The Gaedhilic druids, though probably quite as learned as their continental brethren, were more isolated; and hence we cannot learn so much of their customs from external sources.

There is no doubt that the druids of Gaul and Britain offered human sacrifices; it appears almost certain the Irish druids did not.
Our principal and most reliable information about this religion, is derived from Caesar.

His account of the learning of its druids, of their knowledge of astronomy, physical science, mechanics, arithmetic, and medicine, however highly coloured, is amply corroborated by the casual statements of other authors.[144] He expressly states that they used the Greek character in their writings, and mentions tables found in the camp of the Helvetii written in these characters, containing an account of all the men capable of bearing arms.
It is probable that Irish druidical rites manifested themselves principally in Sun-worship.

The name of Bel, still retained in the Celtic Beltinne, indicates its Phoenician origin; Baal being the name under which they adored that luminary.

It is also remarkable that Grian, which signifies the sun in Irish, resembles an epithet of Apollo given by Virgil,[145] who sometimes styles him Grynaeus.