The canal lock

An original fiction passage set in the nineteenth century.

The barge captain called again from somewhere beyond the wall of mist. Mr Dyer placed his lantern on the stones and approached the mechanism. For a heartbeat, his hand hovered above the iron handle. The water was unusually restless, and he could scarcely see the bow of the vessel. Then the captain shouted that his cargo could not wait, and Mr Dyer pulled the handle towards him.

Identify the phrase which shows that Mr Dyer hesitates before he opens the lock.