  AC susceptibility measurements are presented on the dilute, dipolar coupled,
Ising magnet LiHo$_x$Y$_{1-x}$F$_4$ for a concentration $x = 0.045$. The
frequency and temperature dependences of the susceptibility show characteristic
glassy relaxation. The absorption spectrum is found to broaden with decreasing
temperature suggesting that the material is behaving as a spin glass and not as
an exotic spin liquid as was previously observed. A dynamical scaling analysis
suggests a spin glass transition temperature of 42.6 mK $\pm 2$ mK with an
exponent $z\nu = 7.8 \pm 0.23$.

Disordered Systems and Neural Networks;Statistical Mechanics