[John Leigh, Medical Officer of Health for the City of Manchester.] Autograph 'Copy of Letter to Mr. Cleminshaw' regarding a process used in Manchester for the production of gas, with note on 'Peroxide of Iron' used 'for the purification of Gas'.

4pp., foolscap 8vo. Bifolium. The copy of the letter closely and neatly written over three of the pages, and the note on 'Peroxide of Iron' on the other. In fair condition, on aged paper, with slight damp damage at head (not affecting text). The letter contains a number of deletions and emendations, and begins: 'I am in receipt of your letter of March 19th. Since I wrote you last I have had a letter from Mr Chubb enquiring about the process and our use of it in Manchester. [...] I explained to him that we continued its use at Rochdale Road Station where he saw it at work until we were overtaken by the enormous winter's production of gas the excessive temperature of which owing to our limited power of cooling and condensation rendered a temporary suspension necessary but that we should resume the use of the process as soon as the production diminished somewhat and that in the meantime the Manchester Gas Committee had ordered a very large cooler or condenser to meet the case for next winter.' The letter ends with Leigh discussing the recipient's work ('I have arrived at the conclusion that you should be as unfettered as possible in the power to make your arrangements') and expressing 'entire confidence' in him. The note on 'Peroxide of Iron' begins: 'As nearly as I can ascertain the quantity of Hydrated Peroxide of Iron used for the purification of Gas at both the Stations has been during the past twelve months about 1520 tons.'