Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. In the preparation of accurate estimates concerning the cost of large excavations information regarding the geologic conditions, as obtained by a study of natural features, is necessary. Drill holes and test pits will furnish supplementary geologic information, but without a gen eral knowledge of the geologic conditions it will not be possible for the constructing engineer to answer such questions as the following.