  Proton-proton correlations were observed for the two-proton decays of the
ground states of $^{19}$Mg and $^{16}$Ne. The trajectories of the respective
decay products, $^{17}$Ne+p+p and $^{14}$O+p+p, were measured by using a
tracking technique with microstrip detectors. These data were used to
reconstruct the angular correlations of fragments projected on planes
transverse to the precursor momenta. The measured three-particle correlations
reflect a genuine three-body decay mechanism and allowed us to obtain
spectroscopic information on the precursors with valence protons in the $sd$
shell.
