Copy letter from Lord Kelvin [William Thomson], to General Sir Francis de Winton 'Sir, I shall be much obliged if you will place the enclosed card of invitation before their Royal Highnesses the Duke & Duchess of York and express to them on behalf of myself and the Council the great gratification it would give us and the Fellows of the Society generally if their Royal Highnesses would honour us with their presence on this occasion. I am, your obedient servant, (signed) Kelvin Pres. R.S. [President, Royal Society]'. 18 May 1894