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224   Life and Letters of Francis Galton

amount of dye. Galton felt keenly the need for a standard and permanent
set of colours, and made a suggestion on this point of great value. In 1869
he had been struck by the great variety of permanent colours which are
produced for mosaic work. He had been over the Fabbrica of mosaics
attached to the Vatican and seen their 25,000 numbered trays or bins of
coloured mosaic. He realised at once the opportunity thus afforded not only,
for the establishment of a general colour scale in this country, but, as the
mosaics were manufactured for the representation of human figures among
other things, for skin, hair and eye-colour scales for anthropometric purposes'.
On Feb. 3, 1870, Galton sent the following letter to the Science and Art
Department, South Kensington. I cite from a. rough draft in the Galtoniana:


"Certain scientific inquiries in which I am engaged have brought forcibly before my notice the great desideratum of being able to obtain an accepted standard scale of colours, by reference to which a person's meaning might be expressed with precision whenever he desired to designate a particular hue or tint. The exhibition of such a standard would fall, I venture to say, most legitimately within the province of the South Kensington Museum, and I will now show how very easily and efficiently this desideratum might be supplied. In the Fabbrica of mosaics at the Vatican in Rome there are no less than 25 thousand trays or bins, numbered consecutively, and each filled with cakes of mosaic material, each separate bin being devoted to a different colour. The workers on the mosaics in the Fabbrica send, as they require, to the superintendent of this department for so many pounds weight from such and such specified bins, the colours they want being solely expressed by the numbers attached to the bins. I have read cursory accounts of this large and most remarkable factory and I have visited it myself as an ordinary though much interested sightseer, but I cannot find any full description of its management either in the Art Library of the South Kensington Museum, or elsewhere. However it may be taken for granted that the facts of the case are substantially as I have stated them.

Now I beg to propose that the authorities of the South Kensington Art Department should make application to the Pope for mosaic tablets containing in order specimens of each of their 25 thousand bins to be suspended in the Museum for the purpose of reference as a standard of colour."

Galton then proceeds to Sliscuss the space that such a scale of colour would occupy; if each fragment of mosaic were 1" x 2", the space required would be about ten square yards. Supposing we arranged our tablets in series of 10 in file and 10 in rank, we should have for 20 rows deep, a length of about 52 feet for the scale. For square specimens 2" x 2", which would probably be adequate, with 40 rows deep, the length of the scale would be about seven yards. Galton continues

"It might be disposed as a frieze running along the wall at a height convenient for reference, the bits of mosaic perhaps arranged in tablets of 100 containing 10 ranks and 10 files, with dark lines at the 5th division each way for convenience of immediately ascertaining the number appertaining to each several bit   

The Fabbrica at the Vatican is maintained by the Papal Government solely for the purpose of mosaics for public buildings in the Roman States and for making gifts to foreign potentates. Presents of art works are given in this way that required, I am afraid to say how many separate pieces of material for their construction and that have demanded the lifetime of a skilled artist for their completion. But the series of tablets of which I speak would be far more easily made..

i Many years after Galton's suggestion Professor von Luschan's useful mosaic skin colour scale came into existence. I have also procured mosaics from the Ho f Fabrik in Berlin and formed permanent scales for coat colour in mammals. Galton's proposal was a most fruitful one, and it is to be regretted that it was never carried out in its entirety.