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Darwin Correspondence Project

From G. H. Darwin   8 July 1873

When filled by you the dram measure weighed 281.92 grains & when empty & moist it weighed 226.20 gr.

Therefore you have been using 55.72 gr. as a dram

It should however have been 54.7 gr   So that you have been using a dram too large by 1 gr. of distilled water

G H. D.

July 8. ’73

The weight of fluid used by you at 2 oz was 865.5 gr. on one occasion & 866.5 gr on a second occasion taking the average it was 866 gr. 2 oz: weigh 875 gr.

So that you have been using as 2 ounces an amount of water too small by 9 gr.1

CD annotations

End of letter: ‘July 8th— 1873.’ ink


George was evidently correcting the concentration of one of the solutions that CD used to test the reactions of the leaves of insectivorous plants.


Corrects chemical concentrations CD has been using [in insectivorous plant experimentation].

Letter details

Letter no.
George Howard Darwin
Charles Robert Darwin
Sent from
Source of text
DAR 55: 160–1
Physical description
AmemS 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 8969,” accessed on 4 December 2021,

Also published in The Correspondence of Charles Darwin, vol. 21