Collingwood ^<1>
January 12/6 78

My dear Sir

Will you allow me to ask whether you have any where stated (& if so to give me an exact reference – by title page and line) that “the red & orange portions of the strontium spectrum are crossed by a number of red bands separated by dark spaces” – thus “there is a bright blue line between the orange and yellow, and an orange line in the blue” and also that there is in the lithium spectrum “one intensely brilliant Crimson band in the orange”

These statements which it seem to me so astonishing that I cannot persuade myself that there is not some mistake or that what you have stated has been strangely misunderstood – or they must have given rise to some further notice & development in other quarters.

In the Strontia Spectrum so long ago as 1832 1822* I have noticed the fact of the occurrence of two bright lines in the yellow one much more highly coloured than the other the colours varying (as well as the refrangibility) towards an orange tint – but certainly I saw no “bright blue” line between them: Reconsidering this experiment I have little doubt that the yellow line was due to the presence of muriate of soda in the Mur. Strontia used.

Hoping this will find you well and wishing you many happy returns of the New Year believe me
My dear SirYours very truly
JFW Herschel

*Edinburgh copy this Transactions 1823 ^<2>

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Notes:

1. Hawkhurst, Kent.

2. John Frederick William Herschel, ‘On the Absorption of Light by Coloured Media, and on the Colours of the Prismatic Spectrum Exhibited by Certain Flames …’, Edinburgh Royal Society Transactions, v. 9, 1823, pp.445–460.