The solar-cycle-related (SC) variation, present in the annual means of geomagnetic elements recorded at European geomagnetic observatories between 1952-1980, is discussed in terms of magnetic and electromagnetic induction in the Earth, produced by variations in the external magnetospheric ring current. The vertical component of the SC variation, in which the effect of electromagnetic induction is dominant, has been used to infer information on electrical properties of the underground. The resistance and the inductance of equivalent loops of currents surrounding the observation points have been derived and mapped. The lateral variation of these parameters has been compared with known conductive structures derived from magnetotelluric and deep geomagnetic sounding studies and interpreted in terms of conductors at various depth levels in the crust and mantle.