Actually, it occurred to me an answer for the question I asked on Rav Shach in his answer for the Rambam. I asked from the opinion of R. Nathan on page 53 of Bava Kama. But I remember now that that is not the opinion of the Rambam as I think I also mentioned in my little booklet on Shas in Bava Kama page 19. There it turned out to be an argument between the Rosh and the Rambam. So, in our case on page 6 of Bava Kama where we are asking why the Rambam does not bring the case of his stone that fell from the roof and the roiling pit. the answer of Rav Shach is we would know the rolling pit from the fact that the person in whose domain is the tree and wall that fell is liable if he did nit remove them after being warned by the court. My question n this tis that the one liable for the rolling pit is not the one who placed it in the public domain but rather the one doing the rolling. this is different that case of the person who owns the tree and wall who is liable. The answer is that to the Rambam it would in fact be the person who owns the pit that would be liable; as in the case on page 19 where the person that owns the string attached to the chicken would be liable--------------------------------------------------Actually, it occurred to me an answer for the question I asked on רב שך in his answer for the רמב’’ם. I asked from the opinion of ר' נתן on page 53 of בבא קמא. But I remember now that that is not the opinion of the רמב’’ם as I think I also mentioned in my little booklet on ש''ס in בבא קמא page 19. There it turned out to be an argument between the רא''ש and the רמב’’ם. So, in our case on page 6 of בבא קמא where we are asking why the רמב’’ם does not bring the case of his stone that fell from the roof and the roiling pit. the answer of רב שך is we would know the rolling pit from the fact that the person in whose domain is the tree and wall that fell is liable if he did nit remove them after being warned by the court. My question n this tis that the one liable for the rolling pit is not the one who placed it in theרשות הרבים ,but rather the one doing the rolling. this is different that case of the person who owns the tree and wall who is liable. The answer is that to the רמב’’ם it would in fact be the person who owns the pit that would be liable; as in the case on page 19 where the person that owns the string attached to the chicken would be liable or the owner of the chicken. This one or that one but not both, So on page 6 we can learn from the owner of the wall and tree that fell to either the owner of the owner of the rolling stone or the one who is moving it.