ACCORDING to Earthquake Notes(11, No. 3; January 1940), earthquakes of varying intensity have been recorded from the neighbourhood of Boulder Dam since September 1936. During the first four months twelve shocks were felt, but the frequency increased until during April 1937 forty-five were felt. After this time the frequency increased until during the early part of 1939 there were on average two humanly felt earthquakes a month. The Wood-Anderson seismograph on the spot recorded more than five hundred disturbances during 1938. There has been some discussion among U.S. seismologists of plans for the observation of possible earthquakes in the neighbourhood of two other areas which will probably be similarly loaded. The first is the unfinished Grand Coulee Dam in the State of Washington, and the second is the proposed Shasta Dam near the confluence of the Pit and Sacramento Rivers in northern California. In the latter case there is yet time to obtain information of the seismicity of the area before loading. Similar data were not obtained in the case of the Boulder Dam.