In order to obtain information regarding the horizontal movements at depth special plastic casings were cemented into 6-in.-diameter holes which had been drilled to depths ranging from 200 ft to 500 ft. The alignments of the casings were determined periodically by means of a special instrument. By this method horizontal displacements as small as 1 in. per 100 ft of depth could be detected. In the following sections the details of the field measurements are given. These are followed by a discussion of the results of the observations.

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