The following link has an interesting report of the MIlls expedition in the North of Chile during 1909 and onwards, written by H.D. Curtis
Mill expedition Report (PDF) [2]
Links
[1] http://www.ctio.noao.edu/noao/content/Report-astronomical-conditions-around-Copiapo-1909
[2] http://www.ctio.noao.edu/noao/sites/default/files/misc/Mills%20Report.pdf
[3] http://www.ctio.noao.edu/noao/sites/default/files/field/image/hdc.jpeg