Three or four days ago the Chicago Tribune published the batting averages of the professional base ball players in tabulated form, carefully compiled from the official scores of all League games played during the season...The most important point, however, is one to which the Tribune does not refer at all, in all probability for the reason that it would demonstrate that the White Stockings, although they appear to be on paper, were by no means the strongest batting team in the League. The point referred to is, that no allowance has been made for the fact that while Chicago invariablyPlayed With A "Lively" Ballwhen it had the choice, all the other clubs except the Athletics used a "dead" ball during the entire season. Mr. Meacham, of the Tribune, has on several occasions attributed the defeat of the Chicago Club by the Browns to the soft ball furnished by the latter, which he claimed it was almost impossible to knock base hits out of. Why, then, was no allusion made to this fact in figuring up the averages? Simply because a glance at the record shows that Chicago would have appeared in a very poor light as compared to St. Louis in the matter of willow-wielding...
-St. Louis Globe-Democrat, October 29, 1876
The flip-side of this is, of course, that the dead ball makes the run-prevention numbers of the Brown Stockings look much better. The Chicagos, using a lively ball, didn't give up many more runs than did the Browns. It's a nice try by Mr. Spink but I'm not buying. There is no acceptable argument by which we can say that St. Louis was better than Chicago in 1876.
And just when you think that analyzing 19th century numbers couldn't get any more complicated, I would say that we would have to take the live/dead ball issue into account when applying advanced metrics to the 1876 season. I guess you could treat it like park effects but it does have to be accounted for.