It was real glass, blown by the Druids themselves. It was supposed to aid the wearer in winning lawsuits and securing the favor of kings.
An animal sacred to the Druids was the cat.
"A slender black cat reclining on a chain of old silver" guarded treasure in the old days. For a long time cats were dreaded by the people because they thought human beings had been changed to that form by evil means.
The chief festivals of the Druids fell on four days, celebrating phases of the sun's career. Fires of sacrifice were lighted especially at spring and midsummer holidays, by exception on November 1st.
May Day and November Day were the more important, the beginning and end of summer, yet neither equinoxes nor solstices. The time was divided then not according to sowing and reaping, but by the older method of reckoning from when the herds were turned out to pasture in the spring and brought into the fold again at the approach of winter—by a pastoral rather than an agricultural people.
On the night before Beltaine ("Baal-fire"), the first of May, fires were burned to Baal to celebrate the return of the sun bringing summer. Before sunrise the houses were decked with garlands to gladden the sun when he appeared; a rite which has survived in "going maying." The May-Day fires were used for purification. Cattle were singed by being led near the flames, and sometimes bled that their blood might be offered as a sacrifice for a prosperous season.
"When lo! a flame,
A wavy flame of ruddy light
Leaped up, the farmyard fence above.
And while his children's shout rang high,
His cows the farmer slowly drove
Across the blaze,—he knew not why."
Kickham: St. John's Eve.
A cake was baked in the fire with one piece blacked with charcoal. Whoever got the black piece was thereby marked for sacrifice to Baal, so that, as the ship proceeded in safety after Jonah was cast overboard, the affairs of the group about the May-Eve fire might prosper when it was purged of the one whom Baal designated by lot. Later only the symbol of offering was used, the victim being forced to leap thrice over the flames.
In history it was the day of the coming of good. Partholon, the discoverer and promoter of Ireland, came thither from the other world to stay three hundred years. The gods themselves, the deliverers of Ireland, first arrived there "through the air" on May Day.