In my contribution on the ‘Sematography of Greek Papyri’ (J.H.S. xxii, 1902) I included the Ptolemaic symbol Τ or = 900 among those of whose origin no satisfactory explanation could be offered (p. 138); although on p. 145 I identified the symbol with the later minuscule symbol ‘sampi’ or = 900, and pointed out the improbability of any association of the latter with either Pi or San-Sigma, whether in forms or arithmetical values. For the rest, as I said, ‘we must wait until we are in possession of ante-Ptolemaic documents, or of some facts yet to be supplied by epigraphy.’This paper is the report of a more thorough survey of the field of Greek and general archaeology on all the questions and problems involved in the explanation of the sign. These are in the best sense trivial, lying at the crossing of the ways of nob a few important theories, to which the foremost scholars have recently devoted much investigation—the composition and history of the Greek alphabet, particularly as regards its application for numeration, the enigmatical Tsade, the mutual relations of the ancient alphabets, the antiquity of S. Semitic (Arabian), Minaean, and Sabaean inscriptions, and the place of the Phoenician alphabet in the history of primitive Hellas.