Copy letter from Robert William Frederick Harrison, to Dr Robert Robertson, Royal Gunpowder Factory, Waltham Abbey, Essex Harrison sends thanks for the abstract of Robertson's paper on 'Constants of explosion', which has been set up for the meeting. With reference to his proposal to send 20 copies of table VII of his paper, Harrison suggests that he send 30 to match the 30 proofs of the abstract that will be available at the meeting. 6 February 1906