In Life and Letters of Charles Darwin, volume 2, Darwin's friend Charles Lyell wrote in a letter to him (dated 3rd October 1859):
You enclose your sheets in old MS., so the Post Office very properly charge them as letters, 2 pence extra. I wish all their fines on MS. were worth as much. I paid 4 shillings 6 pence for such wash the other day from Paris, from a man who can prove 300 deluges in the valley of the Seine.
What does Lyell mean by "wash"? Actually, I can't get the meaning of this whole bolded phrase?