Copy letter from Robert William Frederick Harrison, to F C C Nielsen, The Great Northern Telegraph Company Limited, 3 St Helen's Place, E.C. Mr [Robert John] Strutt's paper 'On the least Potential Difference required to Produce Discharge through various Gases' was published in 'Philosophical Transactions [of the Royal Society]', Separate Papers, A, 250, and can be purchased from Messrs Dulau and Company. 20 September 1904