u/Bagheera504

I am working on an historic church and have come upon only what I can describe as horizontal arches. Has anyone heard of this? They are in the side attics between the clerestory interior wall and the top of the exterior wall which is supported by buttresses. It is a classic cathedral layout with a central nave and side aisles running parallel. There are balconies above the side aisles, and within the ceiling structure of those balconies hides two massive aches/trusses. The bottom chord runs about 100 feet parallel to the exterior wall.