Thermal boring device, or subterrene, under development at Los Alamos Scientific Lab, NM, described (W Sullivan rept); device can melt its way through solid rock at 30 inches an hr with some of molten rock being forced into pores and cracks while some hardens into glass sheath on tunnel walls; it is hoped that ultimately such devices will penetrate many mi into earth; project leader J Rowley notes applicability of such boring methods to vehicular tunnels and other large shafts remains to be demonstrated, int; repts Bell Laboratories is also exploring possibility of thermal tunneling; diagram