Copy letter from Robert William Frederick Harrison, to Professor Hugh Longbourne Callendar, Fellow of the Royal Society The paper by C P Butler on 'The Spectrum of Halley's Comet' is short, an accompanied by a plate, the cost of the latter being about £5. Sir Joseph Larmor suggests that the communicator should be informed that the expensive reproduction of the plate is not necessary. Also sending herewith [no enclosures] a copy of the referee's opinion on Dr Havelock's paper on 'Optical Dispersion - an Analysis of its Actual Dependence upon Physical Conditions'. Larmor thinks it is a 'Proceedings [of the Royal Society]' paper. The referee does not want it cut down, although it is 30 pages. 8 November 1910