  We have investigated the magnetic and dielectric properties of orthorhombic
Eu$_{1-y}$Y$_y$MnO$_3$ ($0\leq y\leq 0.6$) single crystals without the presence
of the 4$f$ magnetic moments of the rare-earth ions. In $y\geq 0.2$, the
magnetic-structure driven ferroelectricity is observed. The ferroelectric
transition temperature is steeply reducing with increasing $y$. In $y\geq
0.52$, two ferroelectric phases ($P\parallel a$ and $P\parallel c$) are
coexistent at low temperatures. In these phases, ferroelectricity has different
origin, which is evidenced by the distinctive poling-electric-field dependence
of electric polarization. Namely, the electric polarization along the c axis
($P_c$) is easily saturated by a poling electric field, therefore $P_c$ is
caused by the $bc$ spiral antiferromagnetic order. On the other hand, the
electric polarization along the a axis ($P_a$) is probably attributed to the
collinear $E$-type antiferromagnetic order, because $P_a$ is unsaturated even
in a poling field of $10^6$ V/m.
