The explanatory inscriptions are generally small in size, the letters averaging one-eighth of an inch in height. On B.F. vases they are painted in black; on R.F. vases of the “severe” style, in purple on the black ground, or in black on the red portions; on later R.F. vases, in white. There is no rule for their position, or indeed for their presence; but, as a general rule, it may be said that they are oftener found on the finer and larger vases, and that they are placed in close juxtaposition to the figures to which they refer. The direction in which they are written may be either from left to right or right to left (as generally on Corinthian or Chalcidian vases); on the Panathenaic amphorae are the only known examples of κιονηδόν inscriptions, in which the letters are placed vertically in relation to each other. They are occasionally found on the objects depicted, as on stelae or lavers (see pp. 260, 272), on shields,[2097] or even on the figures themselves.[2098] Signatures of artists are occasionally found on the handle or foot of a vase.[2099] Kretschmer (p. 5) illustrates the practice of employing inscriptions on vases from the art of the Semitic nations. He instances clay vases from Cyprus with painted Phoenician inscriptions,[2100] for which the same pigment is used as for the decoration of the vases themselves. But none of these are likely to be earlier than the first Greek inscriptions, and it is more than probable that the Cypriote Phoenicians borrowed the practice from the Greeks. In order, therefore, to obtain information as to the date of these painted inscriptions, we are entirely dependent upon internal evidence. The importance of these inscriptions may, perhaps, be best realised when it is pointed out that they are one of the chief guides to the age of the vases, and have contributed more than any other feature to the establishment of a scientific classification of the earlier fabrics, as will be fully indicated in the succeeding account. The Greek alphabet, as is well known, is derived from the Phoenician, and this is attested not only by tradition, but by the known existing forms of the latter, the signs being twenty-two in number. The invention of the two double letters, and of the long η and ω, which are purely Greek, was attributed by popular tradition to various personages without any authority. With the question of the introduction of writing into Greece this is not the place to deal. Recent discoveries, especially in Crete, have greatly modified all preconceived notions on the subject, and for the present we are only immediately concerned with the earliest use of the Greek alphabet, as we know it.