The suggestion by Dr. Franklin S. Harris, Jr., that these books be written arose pursuant to the editor's plaints that despite the implicitly or explicitly ack nowledged importance of both aerosols and particulate matter in innumerable domains of technology and human welfare, investigations of these subjects were generally not supported independently of the narrowest conceivable domains of their appli cations. Frank Harris, who has long been a contributor in one of the important domains of aerosol macrophysics, atmospheric optics, challenged the editor to elaborate his views. Ideally, they...