Chromatic scale

Extract from the manuscript lecture by Warren de La Rue on his observations and visual record of the Total Solar Eclipse of 1862, Spain. The lecture was presented at the Royal Society on 10 April 1862.
De La Rue presents reports 'The chromatic scale I here insert contains a selection of the tints painted round my diagram'. Several minutes (probably five) before totality, I entirely removed the dark glass and found the sun's image might be looked at without the slightest inconvenience after reflection by the plain glass'.