Charts. Rio Grande of Mindanao, P. I., Approaches to, including Polloc [or Palak] Harbor and Bongo Island, from survey in 1903 and 1904 by U. S. S. Samar, including survey of Polloc Harbor in 1902 by U. S. S. Annapolis; chart 2055. Scale naut. m.=1.7 in.