Alfred Phillipps Ryder to Faraday   14 September 1860

Royal Commission, | Lights, Buoys, and Beacons, | 7, Millbank Street, S.W. | London. | 14 Sep 60

Private

Dear Sir

I return the enclosed with thanks - I have sent a copy to Adl. Hamilton that he may see how complete a course of experiments you propose to make. My impression as I stated to Mr. Chance at Whitby & since is that the comparisons would be most effective & decisive if the Yacht was stopped anchored if possible about 5 miles off the light a distance which we reached when we were there - And that the ill: app be turned by preconcerted signal.

If you steam about to get views of the diff. phases you probably diminish or increase [the] distance which would affect the accuracy of the comparison - and as at that distance 5m (- a distance to which we should attain for accurate inferences) you would have to steam a considerable distance, from the full action of one set of prisms to that of the other, including the distance necessary for turning such a time would elapse between 2 observations, that the last impression would have faded from the retina - I am aware of the great value of the standard, No. Light but still after a few minutes have elapsed, I think a diff of opinion might arise as to whether the prisms looked at were more or less bright than those that preceded them[.] If you agree with me I feel certain that the plans I suggest could be adopted - and the comparison made rapidly - that no risk should be incurred as respects the passing mariner.

Yours truly | Alfred Ryder