Cambridge | April 25 /53.
Dear Sir,
As you have been experimenting on the conductive powers of various substances,1 I am desirous of knowing whether you could undertake the determination of the conductive powers of certain substances solidified under pressures varying from the atmospheric pressure to 6, or 8000 lbs. per inch. I am now determining the effect of similar pressures on the temperatures of fusion of a variety of substances. We have applied pressures to Spermaceti2 and wax (the only substances we have yet tried) which have produced an increase of 15°Fah;3 in the temperature of liquifaction,4 and I have reason to believe that the conductive powers of these substances may possibly be very much increased when solidified under great pressure. Our experiments will also be continued with a variety of other substances: and what I want to know is whether you would undertake to determine the conductive powers of these substances, specimens of which I would supply you with, solidified under different amounts of pressure. I suggest this to you knowing that you have a delicate apparatus5 ready for the work. The results will have a very important bearing on certain questions in terrestrial physics.
We have the means of forming cylinders of these compressed materials of about 7 or 8 inches long and of which the diameter of a transverse section is 3 inches. You could probably obtain from such cylinders specimens quite large enough for the purpose.
I should be glad to hear from you on this subject as early as may be convenient to you.6 If you would like to undertake the experiments, as I hope you will, I will have some specimens immediately prepared for you.
I may add that should you have to incur any expenses in these experiments I will with pleasure defray it. The Committee for the disposal of the Government grant have behaved very liberally to me respecting the experiments I am carrying on, on the temperatures of fusions.
Yours very grat[eful]ly | W. Hopkins.
RI MS JT/1/TYP/2/603
LT Typescript Only
Experimenting … substances: it was possible that Hopkins was in attendance when Tyndall gave his lecture on 6 January at the RS (see letter 0698, n. 12).
Spermaceti: wax that forms in the head of sperm whales.
15ºFah: fifteen degrees Fahrenheit.
liquifaction: misspelling of liquefaction, the reduction to a liquid state (OED).
a delicate apparatus: this is the ‘ducky little instrument’ Tyndall invented for experiments on conduction (see letter 0638, n. 11).
I should … to you: Tyndall acknowledged receipt of this request in his journal entry of 26 April (JT/2/13b/603) (see letter 0862, n. 7).
Please cite as “Tyndall0753,” in Ɛpsilon: The John Tyndall Collection accessed on