In Irish mythology, the beginning of the summer season for the Tuatha Dé Danann and the Milesians started at Beltain. Great bonfires would mark a time of purification and transition, heralding in the season in the hope of a good harvest later in the year, and were accompanied with ritual acts to protect the people from any harm by Otherworldly spirits, such as those of the Sídhe.
Like the festival of Samhuin, opposite Beltuin on Oct. 31, Beltuin was a time when the Otherworld was seen as particularly close at hand. Early Gaelic sources from around the 10th century state that the druids of the community would create a need-fire on top of a hill on this day and drive the village's cattle through the fires to purify them and bring luck "Eadar dà theine Bhealltuinn" in Scottish Gaelic, 'Between two fires of Beltuin'. In Scotland, boughs of Juniper were sometimes thrown on the fires to add an additional element of purification and blessing to the smoke. People would also pass between the two fires to purify themselves.
The Celts would start their Festivities on the Eve of the day before the Calendar date : Beltuinn start on April 30th., going through May1st., and ending on May 2nd.
Beltane falls within the astrological sign of Taurus the Bull, thereby associating the celebration with the robust life-force of eros in humans and their herds. Given this association, as Beltane nears again, one special aspect of contemporary society comes into chillingly clear focus: our attitude towards cattle – our major source of meat and milk. Beltane was once a time in which one’s cattle were honored in rituals of protection, purification, and fertility.
Cows in ancient Ireland were closely associated with various goddesses, especially those connected to rivers (cattle need to drink an average of 16 gallons of water/day, more for milch cows, so a good water supply is essential ). The cow, along with the vulture and serpent, were the symbols most associated with the Celtic goddess Brigit -- as a Divine cow, her milk was sacred food, drinking it was a “communion” with her, a healing cure, an antidote against poisonous weapons -- until the practice was forbidden in the 12th century, the Irish regarded cow’s milk as so sacred that they even used it instead of water to baptize their children
The Beltaine altar we made in the forest :