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Letter 8260

Darwin, Leonard to Darwin, C. R.

[29 Mar 1872]

Summary

Data relating to experiments; shrinkage of earth on drying.

Transcription

Dear Father

The following is the solid content of the box, which I forgot tomeasure last week.

211.44 Cubic inches

Your affec son. | Leonard Darwin

Iron box of earth.

Measurement after being well dried before the fire. = 180.8 Cubic inches.This shews that it has diminished 10 per cent on the original earth,without taking into account internal shrinking, although cracks werevisible on the surface.f2

DAR 162: 75
CD note:

true

Footnotes

f1
The date is established by CD’s note.
f2
In Earthworms, pp. 161–2, where he gave measurements of dried earth byweight rather than volume, CD concluded that the largest castings wereproduced on the poorest soils, indicating that worms had to swallow agreater amount of earth on poor land in order to obtain enough food.
f3
A further set of calculations, made by George Howard Darwin on the letter,estimates that the loss in volume of the dried earth is approximately116.
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