the water-tube sets being inclined in opposite directions, e.g. crosswise

Full Title

Water-tube boilers of horizontally-inclined type, i.e. the water-tube sets being inclined slightly with respect to the horizontal plane > built-up from water-tube sets in abutting connection with two header boxes in common for all sets, e.g. with flat header boxes > the water-tube sets being inclined in opposite directions, e.g. crosswise