OK, Jeffries power. Some historians who saw Jeffries from ringside rated Jack Dempsy an order of magnitude higher in this department. This has to be taken into acount. Others saw Jeffries as being an equal hitter but one whose style made it less obvious. For me, both sides of the debate are still in the fight.
Jeffries' power is hard to rate. On one hand, he usually fought much smaller men and old ones at that, yet still needed many many rounds to stop them. On the other hand, he did stop some of them with one punch. Something on breaking the ribs: while i don't think 2 or 4 ounce gloves make it easier to score a knockout than 8 or 10oz gloves, i do think it's easier to break a rib, cause a cut or bruise with smaller gloves.
It should be noted that Bob Fitzsimmons did have some fights with 8 oz gloves. The gloves of today would not upset him.
Weren't most of his fights, before but also including the ones with Jeffries with 2 or 4 oz gloves or smaller, though? I wasn't aiming at Fitzsimmons adaptability, but more at the fact that smaller gloves cause more superficial damage, including broken bones.