John Martin is the subject of Marjorie's first book (at least one-third) and she's working on the second. The link below is to the Google Books search for his brother-in-law, Maxwell Simpson, who was in Paris in the 1850's,. The search found Simpson's obituary. (Google makes it easy to select a portion of a page and post it to your blog, but not so easy when there are multiple pages. To read the whole obituary, you'll have to scroll back the pages (and tolerate a lot of discussion of chemistry).
Proceedings of the Royal Society of London By Royal Society (Great Britain):