Reading in a book by 落合淳思 I wonder about (what looks like) the compound verb 益し加える in the sentence 「自は鼻の象形であり、それに声符を益し加えた繁文である。」 (繁文 is used by Ochiai as a technical term for the modern shape of a sinogram that used to have a different shape. Ochiai uses 声符 in the meaning of 音符. The topic is the development of the sinogram 鼻)
I suspect that 益し加える is simply a different way of writing 増し加える, that is ましくわえる. Even then I’d wonder why not simply use 加える? But as it is, why use 益し?
I’d understand the meaning of the sentence as something like“It [鼻] is a hanbun (sinogram with a changed shape) in which 自 is a pictogram of a nose to which a phonetic is added.” What adds 益し to this and why use the graph 益?