Correspondence; published material; spectrum plates and photographs; manuscripts; student notebooks. Correspondence (1901-1959) with colleagues, dealing with experimental physics research, education, publications, and visitors to Mt. Holyoke College. Published materials (1898-1952) consist of reprints, articles, and clippings concerning dielectrics, soft x-rays, discharge rays, chlorine spectra, Raman effect, thermal conductivity, and Laird's dissertation. Chlorine spectrum plates (1900-1901) with related data sheets and photographs of experiments. Manuscripts (1900-1953) by others, annotated by Laird, on thermoluminescence, Raman effect, and ultra-violet rays. Laird's student notebooks (1897-1898) while at Bryn Mawr College on Arthur S. Mackenzie's lectures on mechanics, optics, electricity, and magnetism, and Edgar Buckingham's lectures on thermodynamics. Correspondents include: Niels Bohr, Arthur H. Compton, Arthur J. Dempster, Theodore Lyman, Arthur S. Mackenzie, Dayton C. Miller, and Robert A. Millikan.