Shabbos Daf 98 שבת דַף 98

It was taught in a Baraisa that if one throws an object from one reshus harabim to another reshus harabim and there is a reshus hayahchid between them, if the object travelled four amos through the reshus harabim, he is liable. If it travelled less than four amos, he is exempt.

The Gemara says the Tanna is coming to teach that רשויות מצטרפות, two identical domains combine for one to be liable for hotza’ah. Meaning, even if it flew two amos in one reshus harabim and two amos in the second reshus harabim. Additionally, we see from here that we do not say  קלוטה כמה שהונחה, that something contained in the airspace of a reshus, is legally viewed as if it has come to rest there, because if indeed we view it as it had landed, the thrower would have been liable, even if it travelled less than four amos, because he transferred it from the reshus harabim into the reshus hayachid.

It was said in the name of Rav that one who transfers an object four amos in a roofed reshus harabim (רשות הרבים מקורה) is exempt, because a roofed reshus harabim does not resemble the encampment in the desert, which is where we learn out the melocho of hotza’ah.

The Gemara questions this ruling since the wagons in the desert, which were used to carry the kerashim, were considered roofed because of the kerashim (beams) placed on them, and Rav said in the name of Rebbe Chiya that the areas beneath the wagons, between them, and the area to the sides, had the status of a reshus harabim. How could the area beneath have the status of a reshus harabim if the wagons were roofed?

The Gemara clarifies that the area beneath the wagons, five amos in length, is referring to a nearly one amah gap of open space in the middle of the wagon, when two stacks of kerashim  were placed at the front of the wagon and two stacks of kerashim were placed at the rear, with each stack being an amah in width.

A Baraisa introduces a machlokes Tannaim regarding the shape of the kerashim.