The great winged man-lions from Mesopotamia are some of the most conspicuous and most wonderful objects in the British Museum. When visiting that museum last September I was greatly interested as a geologist in examining the kind of rock of which they are composed. This rock is, I suppose, usually taken to be a granite, but it is not an igneous rock. On the contrary, it is of sedimentary origin, a felspathic sandstone (arkose or sparagmite) of very coarse grain, almost bordering on a conglomerate. In the most characteristic variety, from the palace of Sargon, the chief constituentis white quartz in lumps varying in size between that of a hazel-nut and an apple (see Fig. 1). These are embedded in a cement of coarse-grained sparagmite. A notable peculiarity is thatthe fragments of quartz have very irregular contours, giving the appearance of an invasion of the larger fragments by the groundmass. In other varieties (Palace of Assurbanipal) the fragments of quartz are smaller and may in some cases show no distinction from the quartz-grains of the groundmass.