L.- mercurial barometer. R. - sling psychrometer.
In: The Aims and Methods of Meteorological Work by Cleveland Abbe. In: Maryland
Weather Service, Johns Hopkins Press, Baltimore, 1899. Volume I. Page 306.
Image ID: wea00916, NOAA's National Weather Service (NWS) Collection Photographer: Archival Photograph by Mr. Sean Linehan, NOS, NGS
