I read the way to tell if a bear is a black bear or a grizzly is to climb up a tree. If it climbs up after you it's a black bear. If it pulls the tree out of the ground it's a grizzly.
I haven't read the book, but saw the movie with Clint Walker (remember, 'Cheyenne'). It's an old movie but was very graphic for it's time. This plan is to open up a "four-legged highway" from Yellowstone southward. There was an incident here recently where two hunters were attacked by a juvenile griz, about 800 pounds. The bear was holding one of the hunters down and then went after the other. Fortunately he had a .45 that fit nicely in the bear's mouth and he was able to pull the trigger as the shell exploded upward.
LOLOL. Beats the bell-an-pepper method, I guess!