Ok, keep clicking to get to the source of the photo…
And then (and this is important if this format drives you crazy like it did me–for those of you, likely most of you, that already figured it out-ignore the following),
you need to go to the top left hand corner and adjust the zoom… and then click on red box imposed over the miniture image in the left corner below the zoom setting. Then with your mouse still clicked, move that little box around. It will shift the larger image (zoomed) around so you can see segments of the image in better detail.
It seriously took me months to figure this out. Clearly not something I should be boasting about but it is true.
This painting is remarkable–and not. I would like to think the artist tried to accurately capture what he saw. The source cite says that it was complete while the painter, Edouart, was a member of a hunting party in 1857 to present to Mendocino County.