A Manual Of Photography

THE COLOURING MATTER OF FLOWERS. 71 « Hed Poppy : Papaver Rheum?—Among the vegetable colours totally destroyed by light, or which leave no residual tint at least when fresh prepared, perhaps the two most nch a beautiful are those of the red poppy and the double purple groundsel (Senecio splendent). The former owes its red colour in all probability to free carbonic acid or some other (as the acetic), completely expelled by drying : for the colour its tincture imparts to paper, instead of red, is a fine blue very slig i y verging on slate-blue. But it has by no means the ordinary chemical characters of blue vegetable colours. Carbonate of soda, for instance, does not in the least degree turn the expresse juice green ; and when washed with the mixture, a paper results If a light alate-grey, hardly at all inclining to green The bl® tincture is considerably sensitive, and from the richness of tone and the absence of residual tint, paper stained with it affords photographic impressions of great beauty and å^ d some of which will be found among the collection submitted with this paper for inspection... “Sea Jo splendent Thia flower yields a rich Purple nice in great abundance and of surprising intensi y. .,.V, exceed the rich and velvety tint of paper tin e w i - It is, however, not very sensible to light, and many weeks a necessary to obtain a good photographic impression. In the progress of my own researches on this subiect, 1 ton that the green colouring matter of the leaves of herbaceous plants, when spread upon paper, changed with tolerable rapid! when exposed to sunshine. There are, however, some ver) curious points connected with the phenomena of t ^0^^clanges which demand a far more extensive investigation than tliey yet received. , . „ I find that the juices taken from the leaves in the spr•g, change more rapidly than when expressed from the sanie P1" in the autumn ; and the juices of those flowering p an have been cultivated under the artificial circumstances^ a store-house, or conservatory, are more readily affected such as are grown in the open an. Many of the expo - just described furnish very instructive examples of the opera- tions of the solar rays upon organic bodies, from which we mav deduce important truths connected with natural phenomena. There are several other very curious observations made by this eminent experimentalist, which might with much propriety have been included in this section Many of these will find a place in the scientific details; and the formation of precipitates on glass plates will be described in the chapter devoted to their consideration.