Analysis of Cetacean

Out of Fisherman’s Wharf, San Francisco, Sunday, early,
  our vessel, bow to stern, some sixty-three feet,
  to observe Blue Whales -and we did, off the Farallones.

They were swimming slowly, and rose at a shallow angle
(they were grey as slate with white mottling, dorsals tiny and stubby,
  with broad flat heads one quarter their overall body-lengths).

They blew as soon as their heads began to break the surface.
  The blows were as straight and slim as upright columns
  rising to thirty feet in vertical sprays.

Then their heads disappeared underwater, and the lengthy, rolling
expanse of their backs hove into our view -about twenty feet longer
  than the vessel herself.

And then the diminutive dorsals
showed briefly, after the blows had dispersed and the heads had gone under
            gone under

Then they arched their backs, then arched their tail stocks ready for diving.
            for diving.

Then the flukes were visible just before the creatures vanished,
  Slipping into the deep again, at a shallow angle.