881. Measuring Ditches and Valleys

Shabbos 28:12

The previous halacha (about measuring the width of a ditch that is up to 4,000 cubits deep) applies when a plumb line (which measures verticals) can be lowered straight down because in such a case the walls of the ditch cannot be used. However, if a plumb line cannot be lowered straight down, the surveyors should only measure the width of the ditch using the rope when the ditch is 2,000 cubits deep or less.

Shabbos 28:13

If a valley has a gradual slope, the surveyors should go down and up, measuring its approximate width. If the valley is more than 50 cubits wide - and therefore unable to be measured using the 50-cubit rope, the surveyors should go somewhere the gap can be spanned, measure it there, then return parallel from that spot to where they were measuring and resume.