Has been with Philip Melvill of the East India Co. discussing the printing of the observations. Would it be a good use of JH's photographic papers to take a reverse of William Parsons' (3rd Earl of Rosse) drawings of nebulae? Cannot obtain Nicolas Clement-Desormes's or John Sharpe's papers. Doubts if the mode of measuring latent heat hitherto used can be recommended for accuracy.