The two verniers on the azimuth circle having been read, the magnet is then inverted, i.e.
These may be used in either the upright or the inverted position.
4 represents the inverted image seen in the telescope.
It varies in colour, but a black mark on the head like an inverted V remains nearly always visible.
These, being no longer stoved in an inverted position, as had been the habit before Shirozaemons time, were not disfigured by the bare, blistered lips of their predecessors.