To derive useful information from the crustal movement records it is necessary to combine the best attainable precision in measurement (1 · 10 9) with long term stability (10 8 sec). It appears that the maintenance of stability, and the calibration and determination of the sensitivity of the intrumentations can best be achieved by operating a number of instruments, each of which is based on an entirely different principle, but measuring the same or a related geophysical quantity, such as strain, tilt, gravity. The development in Australia of the facilities for the measurement of crustal movement will be reviewed and, in particular, an outline of the results achieved at Armidale will be given. It is expected that if the earth's crust be made up of plates that have an effective elastic rigidity for tidal periods, the actual strain near the edge of a plate would depart from the strain predicted on the basis of a crustal model which has assumed a non-tesselated surface of the earth. In other words, it is expected that plate boundaries or major fractures in the earth's crust, may be identified by the concentration of an irregular strain pattern along the boundaries. Such a pattern is to be sought with mobile strain-measuring equipment which has been developed. Currently, there is no information available about the total tidal stress patterns in the crust and any information will be of value in understanding the response of the crust to tidal deformations. In particular, it seems that the measurement of tidal deformations in the crust could have distinct relevance to the lateral movement of plates such as has been postulated in the theory of plate tectonics. For example, it is known from seismic and gravity information that the region 70–250 km is of low rigidity, lower density and a low “figure of merit” ( Q), and that tidal deformations lead to a release of 2.75 · 10 19 erg/sec. This figure is accurately known. The uncertainties arise as to where precisely the energy is released. The atmosphere and the oceans account for a significant fraction, and the core as an energy sink is untenable because it leads to restrictive core—mantle coupling conditions and in all cases is inadequate. This raises the possibility of re-examining the mantle and specifically the low velocity layer as a tidal energy sink — i.e., a fraction of the tidal energy of 2 · 10 19 erg/sec would be liberated in the depth range of 70–250 km. The two questions to be asked and answered are: 1. (1) Is the lag in the tidal phase across the country constant? 2. (2) Is the phase change related to the surface geology or known tectonics? To progress with answers to these questions, basic measurements of the tidal strains at an array of stations are necessary.