Originally contracted for five weeks between April and June 1799 to catalogue and arrange the important mineral collection begun by Georgiana, Duchess of Devonshire, then partly housed in Chiswick, he also arranged the mineral collection of Lady Henrietta of Bessborough (Georgiana's sister) in Cavendish Square at the same time.
Awalnya dikontrak selama lima minggu antara April dan Juni 1799 untuk pembuatan katalog dan mengatur koleksi batuan mineral penting diawali oleh Georgiana, Duchess of Devonshire, kemudian bertempat di Chiswick, ia juga mengatur koleksi batuan mineral Lady Henrietta dari Bessborough (saudari Georgiana) di Cavendish Square pada waktu yang sama.