PROFESSOR TYNDALL, LL. D., F. R. S.
With regard to the use of alcohol and tobacco, I do not think any general rule can be laid down. Some powerful thinkers are very considerable smokers, while other powerful thinkers would have been damaged, if not ruined, by the practice. A similar remark applies in the case of alcohol. In my opinion, the man is happiest who is so organised as to be able to dispense with the use of both.
JOHN TYNDALL.
Feb. 14, 1882.