  We measured Doppler shifts of three bright spectral lines in the X-ray
emission from Cygnus X-3 as recorded by the Chandra X-Ray Observatory. Doppler
shifts of lines associated with Si XIV and S XVI exhibit orbital modulation.
The magnitude and phasing of this modulation relative to the orbital ephemeris
indicate the location of the source of this emission within the wind emanating
from the compact object's companion. These observations enable us to make an
indirect measurement of the separation of the two stars. Under certain
assumptions our observation of a line associated with Fe XXV also limits the
mass of the compact object M < 3.6 MSun.
