# From Leonard Darwin   [29 March 1872]1

Dear Father

The following is the solid content of the box, which I forgot to measure 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 were visible on the surface.2

## CD note:

March. 29.1872.

Leonard

Earth dug out of ground & thrown up in fortification   increase 〈of〉 above $\frac{1}{12}$th of bulk.—3

## Footnotes

The date is established by CD’s note.
In Earthworms, pp. 161–2, where he gave measurements of dried earth by weight rather than volume, CD concluded that the largest castings were produced on the poorest soils, indicating that worms had to swallow a greater amount of earth on poor land in order to obtain enough food.
A further set of calculations, made by George Howard Darwin on the letter, estimates that the loss in volume of the dried earth is approximately $\frac{1}{16}$.

## Summary

Data relating to experiments; shrinkage of earth on drying.

## Letter details

Letter no.
DCP-LETT-8260
From
Leonard Darwin
To
Charles Robert Darwin
Sent from
unstated
Source of text
DAR 162: 75
Physical description
2pp damaged †, †(by G.H. Darwin)