  New low frequency ac susceptibility measurements on two different spin
glasses show that cooling/heating the sample at a constant rate yields an
essentially reversible (but rate dependent) X(T) curve; a downward relaxation
of X occurs during a temporary stop at constant temperature (ageing). Two main
features of our results are: (i)when cooling is resumed after such a stop, X
goes back to the reversible curve (chaos) (ii) upon re-heating, X perfectly
traces the previous ageing history (memory). We discuss implications of our
results for a real space (as opposed to phase space) picture of spin glasses.
