In the year 1842 I discovered that the luminous and brilliant lines in the spectrum of certain flames, since called vapour lines, corresponded to certain dark lines in the solar spectrum.

This observation was made for the first time by the spectrum produced by the deflagration of nitre, and I afterwards found that this was a property belonging to every such flame.

This result was obtained from experiments made at St Andrews in 1842, on nearly 180 substances, deflagrated in a platina cup by a mixture of oxygen and coal gas. A notice of these experiments was read at the meeting of the British Association at Manchester in 1842. The journal containing them was laid before the Physical Section, and one or two of the more interesting results were published in the reports of the Association for that year.