To these revelations by the spade there should be added various contributions of the pen, which, together with the old materials, make possible the study of Hittite remains upon an historical rather than a purely archæological basis. We might indeed make some general inferences from the results of these researches, but it will be wise to keep ever in view the geographical conditions, and never to assume collateral development among the various branches of the Hittite peoples whose lands were physically so disunited. Evidence affecting one state in the north of Syria may be applied with some surety to its neighbours; but it may not be applicable beyond the Taurus. No published accounts enable us to test the antiquity of Hittite settlements upon the tableland of Asia Minor, and it is doubtful if even the necessary soundings have been made. For the middle period, however, the difficulty is less, where history shows that the influence of the Hatti administered from Boghaz-Keui must have predominated in the north of Syria, and contemporaneity of development may therefore be inferred. But when we come to the inferior limit of date the same difficulty (the possibility of independent development) is reopened, for, in the absence of positive material evidence to the contrary, the Assyrian arms seem never to have passed the Halys even while Assyrian influences were dominant in Syria. On the other hand, as we have seen in the previous chapters, we have to take into account the possible influence of the new civilisations, like that of the Phrygians, which had meanwhile been developing upon the tableland. One thing at any rate seems clear, that no Hittite monuments of Asia Minor can well be later than the period of Phrygian domination in the eighth century B.C.,[135] so that in the end a general parallel is suggested with the closing dates afforded from Assyrian history.