From Edward Frankland   15 April 1874

Dear M^r. Darwin

Herewith I send you a small quantity of phosphate of lime free from animal matter.¹ It has not exactly the composition of bone-ash but nearly so. If you would like to try real bone ash, put a small piece of bone in the fire & after an hour or so rake it out, pick out the white portions & crush them to a convenient form for your experiments. I should not anticipate that Drosera could deal with bone-ash so prepared, because it has been made less easily assimilable by the fire.² The enclosed sample has been precipitated from solution & is therefore in the most favourable condition for assimilation.

I shall be glad to send you some weak sewage water when you are ready for it.³

Believe me | Yours sincerely | E. Frankland