beyond the green line _b_. This solution was _deep emerald-green_, and even dilution did not alter the phenomena. The _acid_ alcoholic solution was as deeply green as the last, but gave only the sharp broad absorption-band in the red, and two very faint ghostly bands in the position described above of the D and _b_ lines respectively. Further additional researches on the chlorophyll of plants furnished curious results, the chlorophyll being dissolved out by alcohol, digested for some hours, and without heat; some plants being fresh, and others dried. Five classes of phenomena exhibited themselves, but _all_ agreed in having the red absorption-band broad, sharp, and well defined, some having this one band only, the Lilac being of this type. There are two classes in which two absorption-bands occur. One has the red and the orange bands, of which the Fuchsia, Guelder-rose, and Tansy are examples; another, in which the red and the green bands are alone co-existent. Ivy is the type of the class, and it is immaterial whether we take last year’s leaves or those of the early spring; the results are the same. The fourth class consists of the two former spectra superposed. Three lines occur, the red, the orange, and the green bands, at C, D, and _b_, as before. This is by far the largest class, and I have thirty or forty examples of it. _Œnothera biennis_, Laurestinus, &c., are types with the ethereal solution of the leaves of Red Bark. The fifth class consists of those having properties similar to the alcoholic solution of Red Bark described. But I only found eight of these, and not all equal in colour power, namely: Berberry, Sloe, Tea, Hyoscyamus, Digitalis, Senna, and Red Bark. The results obtained appeared at the time to be well worth following up to a more practical conclusion than that arrived at. It should be noted that in the preparation of vegetable colouring matters for the micro-spectroscope, care must be taken to employ only a small quantity of spirits of wine to filter the solution, and evaporate it at once to dryness at a very gentle heat, otherwise if we attempt to keep the colouring matters in a fluid state they quickly decompose. It is necessary also to employ various re-agents in developing characteristic spectra. The most valuable re-agent is sulphite of soda. This admits of the division of colours into groups. It is better to use a dilute alcoholic solution for the extraction of colour from plants, and to observe the spectrum in a column of about three-quarters of an inch in height. By this means it is quite possible to ascertain that the spectrum of chlorophyll presents seven distinct absorption bands. For further information on this interesting subject I must refer the reader to Mr. Sorby’s paper “On a Definite Method of Qualitative Analysis of Vegetable and Animal Colouring Matter by means of the Spectrum Microscope,” “Proc. Roy. Soc.,” No. 92, 1867. CHAPTER IV.