Royal Institution of Great Britain | 16th March 1863.
My dear Sir John,
During the whole of the Friday fixed for Mr Herschel’s lecture1 our lecture room will be at his disposal. Trained assistants shall be here to suspend his diagrams and otherwise execute his commands.
The most common error of our lecturers is the accumulating of more matter than can be made to fit within an hour—Our audience comes wound up for an hour, but it is not wise to push them much beyond this.
If Mr. Herschel can turn our electric lamp to account in the way of illustration it shall be also got ready for him. We can reproduce almost any optical effect by means of it. However it is best that he should not swerve from his own independent course.
Imagine the pressure on every square yard of the bed of a glacier say 1000 feet thick— Such a tool urged forward by the force from behind must exert an enormous rasping action. In fact the glacier rivers of Switzerland are loaded to an extent never observed in non glacial streams. The delta of the Rhone has been ploughed out of the mountains by the Rhone glacier.2
I cannot help thinking that such an agency active for ages must profoundly affect the contour of a country.3
Yours ever truly | John Tyndall.
RI MS JT/1/TYP/2/523
the Friday fixed for Mr. Herschel’s lecture: Alexander Herschel; see letter 1958, n. 6.
Rhone glacier: see letter 1915, n. 2.
I cannot help… contour of a country: here Tyndall was responding to Herschel’s comment from the previous letter (1981): ‘The view taken of the enormous degrading & grinding power of Continental ice in Lyell’s last work struck me exceedingly. How far it is original or new I can not of course say—but put in that form it struck me as quite such a new power in Geology’.
Please cite as “Tyndall1983,” in Ɛpsilon: The John Tyndall Collection accessed on