. . . "Pritchard's wedge photometer"@en . "Pritchard's wedge photometer" . . . . . "Pritchard's Wedge Photometer. By S.P. Langley, C.A. Young, and E.C. Pickering. (Investigations on Light and Heat published with appropriation from the Rumford Fund.) [From the Memoirs of the American Academy of Arts and Sciences.]"@en . . . . . . . "Pritchard's Wedge Photometer : By S.P. Langley, C.A. Young, and E.C. Pickering. (Investigations on Light and Heat published with Appropriation from the Rumford Fund.)" . . . "Pritchard's Wedge Photometer" . . . . .