The green Westmorland slate triglyphs somewhat unusually step up with the raked mouldings of the pediment and appear to support the roof of the portico.  These three sided triglyphs tie together the mouldings on the inside of the building with those on the outside through the open pediment.  This step in the position of frieze between inside and outside recalls the step between the outer Doric mouldings and the inner Ionic mouldings at the Propylaia in Athens built in 437‑432 B.C. by the architect Mnesikles – the first recorded art gallery in the western world.