Copy letter from Robert William Frederick Harrison, to Edwin Bale, Art Director, Cassell & Company Limited, Belle Sauvage Yard, Ludgate Hill, E.C. Wishes to know whether Cassells are not undertaking colour printing by the three photographic process. Sometimes have plates to execute for the 'Philosophical Transactions [of the Royal Society]' which need to be well done, and currently has a particular case for the reproduction of some coloured plates in the nature of spectra. Wishes to be told if it is of any use applying to Cassells for such work. 6 May 1898