  We study the consequences of in-plane (D_p) and out-of-plane (D_z)
Dzyaloshinsky-Moriya (DM) interactions on the thermodynamic properties of
spin-1/2} Heisenberg model on the kagome lattice using numerical linked cluster
expansions and exact diagonalization, and contrast them with those of other
perturbations such as exchange anisotropy and dilution. We find that different
combinations of the DM anisotropies lead to a wide variety of thermodynamic
behavior, which are quite distinct from those of most other perturbations. We
argue that the sudden upturn seen experimentally in the susceptibility of the
material ZnCu3(OH)6Cl2 can be understood in terms of Dzyaloshinsky-Moriya
anisotropies with D_p>|D_z|. We also show that the measured specific heat of
the material puts further constraints on the allowed DM parameters.
