  We have investigated the pitch angle ($\psi$) of the spiral arms of galaxies
in the Hubble Space Telescope COSMOS field. The sample consists of 102 face-on
galaxies with a two-armed pattern at a mean redshift $\langle z \rangle \approx
0.5$. The typical values of $\psi$ in the spiral arms of distant galaxies are
shown to be close to those for nearby spiral galaxies. Within one galaxy the
scatter of $\psi$ for different arms is, on average, half the mean pitch angle.
In the $z$ range from 1 to 0 we have found a tendency for $\psi$ to decrease.
Our analysis of the $\psi$ distributions in galaxies at different redshifts is
consistent with the assumption that in most of the galaxies at $z \leq 0.5$ the
spiral arms are tidal in origin or they arose from transient recurrent
instabilities in their disks.
