Deaths from a variety of diseases are shown on this map of Oakland by symbols. For example: a black triangle is used for an incidence of smallpox; a plus sign denotes a death from scarlet fever; a black square is the symbol for diphtheria, etc., etc. Where a particular death has occurred, the relevant symbol is used at that location. In addition to these death symbols, the City Engineer, T.W. Morgan has used wavy lines to describe intercepting sewers, dotted lines for regular sewers, and a dark heavy line for main lake sewers. "Index of mortality from prevalent zymotic diseases during 1878, 1879, 1880...