Blanckenhorn’s fault-lines lie for the most part within the area covered by the alluvial deposits and the water of the lake, so that for want of exposures it is in most cases impossible to directly disprove their existence, although strong presumptive evidence against them can be adduced. The fault along the east side, however, is shown as closely following the junction line of the desert and the cultivated land, but everywhere along this line we found the marls and limestones of the Ravine beds passing regularly from the desert under the cultivated lands, without any sort of break or dislocation. Moreover, an examination of the desert ridge to the east disproved the existence of any faulting on the desert side, while the appearance of the same beds in the ravine of El Bats, a few kilometres to the west, proved the continuity of the beds under the cultivated alluvium in this direction. Certainly no fault exists along this side of the Fayûm. Similarly with regard to the fault shown as running from the west end of the lake along the west side of the Fayûm cultivation into the basin of Gharaq; although the desert margin along this side of the Fayûm cultivation has not been so closely surveyed as that on the east side, no evidence in favour of the existence of faults was met with in the particular localities examined. With regard to the third main bounding fault, considered by Blanckenhorn to run throughout the length of the Birket el Qurûn and to be continued eastwards, possibly to the Nile Valley and at least to join the fault on the east side of the cultivation, we need only say that an examination of the desert near Tamia disproves its existence at that end; while it is difficult to imagine that a fault could traverse the lake from end to end without revealing its presence in the island Geziret el Qorn or in one or other of the promontories which jut out so far into the lake from its northern shore. Everywhere the strata are undisturbed and occupy their normal stratigraphical level and position.