Letter, from Sir John Herschel to William John Macquorn Rankine, dated at Collingwood Signed with sender's name by an amanuensis. Writes to thank William John Macquorn Rankine for the paper on the thermodynamic theory of waves he sent; John Frederick William Herschel is too ill to respond or even to deal with the analysis in the paper. Nonetheless, John Frederick William Herschel does make some suggestions for William John Macquorn Rankine's consideration. 14 January 1871