Collingwood 1
May 14/41
My dear sir
Among a vast No of trials I have been lately making on vegetable juices I have lighted upon one of a very singular character – quite contrary to the analogy of all the rest except [illegible deletion]. I send you a specimen (No 1040) 2 in which A is the original colour of the paper before exposure to light & B that assumed after long exposure. The intermediate portion has been subjected to the action of the spectrum. The scale VYR at the side shews the extent of the luminous spectrum exclusive of the sun’s diameter – and you will observe that the Red rays have no effect the yellow scarce perceptible the Indigo-blue the maximum and that the action extends far beyond the luminous spectrum. In a word the resemblance is great to the spectral-impression on paper prepared with the Nitrate of Silver and Hydriod. of Potash – and it agrees with the argentine spectm in being darker than the ground colour and in the tone of tint.
I have been so very unlucky as to lose your paper about the Calotype. 3 I believe I lent it & it has not been returned – have you still one to spare?
Believe me Dear sir Yours very truly
JFW Herschel
PS. The juice is that of a Cape plant I brought home with me I believe a new species of Anthericum. I have only a single growing specimen & am very unwilling to destroy it and as it is but a small plant it is with difficulty I collected by bleeding enough juice to colour this paper – I shall therefore beg the favor of you to reinclose it at your leisure.
PS I enclose 4 another spectm on yellow paper No 1042 which exhibits a curious contrast with No 1040. It has just turned up.
Most yellow juices I have hitherto tried have proved nearly insensible This on the contrary is very sensible – the spectrum annexed was impressed in 55 minutes.
H. F. Talbot Esqr
Lacock Abbey
Chippenham
Wilts
31 Sackville Street 5
London
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