Copy letter from [Robert William Frederick Harrison, Assistant Secretary of the Royal Society]; to an unknown correspondent 'It has been suggested that a short summary of the results and conclusions arrived at would add to the usefulness of the paper. It has also been pointed out that the words "forced vibration" are used in this paper in a sense that is not in accordance with general usage.' [The paper in question is illegible, along with any details of its author or the copy letter's recipient.] [14 January 1919]