36. The differences in the statements of Le Conte, Bartlett, Parke, Miehler, Irwin, and Ainsa, relative to the original site of the meteoritic masses of Tucson, are all such as might easily result from simple errors of printing or interpretation: the masses have been known for centuries: they were found in a pass called Los Muchachos, which is between Tucson and Tubac, and is on the eastern side of the road: other masses of various sizes are said to be still in the pass. The results of the analyses made by Smith, Genth and Brush, show that, besides small proportions of schreibersite and chromite, there is a varying proportion (8 to 10 per cent.) of stony matter included in the nickel-iron: they are consistent with the stony matter being a lime-olivine, having approximately the per-eentage composition FeO 24·07, MgO 27·37, CaO 8·67, Na₂O 2·15, K₂O 1·26, and SiO₂ 36·48, and with the nickel-iron being composed of Fe 89·89, Ni 9·58, Co 0·49 and Cu 0·04.