The paper describes a new method of driving tunnels through granular soils above or below the water table using a mechanical tunneling machine within which the face is supported by a thixotropic slurry. The devlopment of the system and the results of the experimental tunnel drive at New Cross are reported. This approach to the problem may be said to combine the techniques of clay and digger-shield tunneling, slurry-trench walling, and oil-well drilling. The machine used in the trials is readily covertible for use as a conventional tunneling machine for excavating in either consolidated gravels or in cohesive soils such as the London clay. Methods of organizing and financing development work of this nature are discussed.