“After that came Caisin, son of Naeman, with great joy to [visit] Finnian. And he offered himself to him and complained to him that the king of Fotharta was demanding gold from him for his liberation. “How much,” said Finnian, “asketh he?” “He would accept an ounce of gold,” said Caisin. He [Finnian] weighed after that the ring (and there was found an ounce of gold[455]) in it. Caisin gave it for his liberation.”
I am indebted for this valuable reference, which also enables us to form an idea of the relative value of gold and silver in early Ireland, to the Rev. B. Mac Carthy, D.D., of Youghal.
But there is another weight called crosoch (crosóg or crosach), found in the most ancient poems. For instance in Cuchulaind the brooch of Queen Medbh, “My spear brooch of gold which weighs thirty ungas, and thirty half ungas, and thirty crossachs and thirty quarter [crossachs].” (O’Curry, Manners and Customs, Vol. III. p. 102.) The weight of a crosoch we learn from a gloss quoted by O’Donovan (Supplement to O’Reilly’s Dictionary) from MS. R. I. A., No. 35, 5. 49.
da pinginn agas cetrime pinginne isin lacht caerach i, crosóg[456].
“Two pinginns and a fourth of a pinginn are a milk of a sheep, i.e. a crosóg.” Since 1 pinginn = 8 grs. wheat therefore a crosóg = 18 grs. wheat or 13·5 grs. Troy.
There are accordingly 32 crosochs in the unga of the Brehon Laws.
Inspection at once shows that the crosoch must have belonged to a different system, on which either the system of ungas and screapalls was grafted or vice versa. The expulsion of the crosoch from the later Irish shows that the first alternative is the true one.
Again, it is certain that the unga and screapall were borrowed from the Roman system, probably before the time of Constantine, as after his time the solidus became universal throughout the Empire, and has left its impress everywhere.
The crosoch therefore must be non-Roman, i.e. belong to the native population.
Above we saw that it was used along with ungas and half ungas in describing Medbh’s Fibula. Here is historical evidence of its use in the weighing of gold ornaments.