adv. & prep. [ Cf. Along. ] Lengthwise; along. [ Archaic ] [ 1913 Webster ]

The doors were all of adamants eterne,
I-clenched overthwart and endelong
With iron tough. Chaucer. [ 1913 Webster ]

He pricketh endelong the large space. Chaucer. [ 1913 Webster ]

To thrust the raft endlong across the moat. Sir W. Scott. [ 1913 Webster ]