The hikers descend on the mountain.
Some cyclists are riding down a mountain.
Hikers are on foot and cyclists are on bikes.
exists e1 x1 x2.(n_mountain(x2) & n_hiker(x1) & on(e1,x2) & Actor(e1,x1) & v_descend(e1))
exists e1 x1 x2.(down(e1,x2) & n_mountain(x2) & Actor(e1,x1) & v_ride(e1) & n_cyclist(x1))