The Hand of Man is considered by Stieglitz to be one of his most seminal images. Made while standing on the back of a train as it entered the rail yard of the Long Island City station, the image has long been widely interpreted, always with a view to the symbolic nature of the machine and what might become of it in man’s hands at the center of those interpretations. The allegorical masterpiece presents a dual message about transformation and power. The image itself functions as an emotional retelling of industrial man’s surging growth and the effect of that growth upon the environment. Additionally, imbedded in the process of creating such an image, is Stieglitz’s lifelong advocacy for the art of photography: an art in which the hand of man when guided by the sensibility of an artist capable of presenting an emotional truth using a mechanical camera. Made in 1902, Stieglitz immediately produced an exhibition print for the show at the National Arts Club in New York that coincided with the founding of the Photo-Secession, all in the same year of 1902. He then went on to include the image in the inaugural issue of Camera Work in January, 1903. Stieglitz included The Hand of Man a second time in Camera Work in no. 36, October 1911, pl. XIII, this time on tissue. 
Doty, Robert M. Photo-secession: Photography As a Fine Art. N.Y: Eastman, 1960. plate VII.
Frank, Waldo D. America and Alfred Stieglitz: A Collective Portrait. New York: Aperture, 1979. pl. 99
Greenough, Sarah, and Alfred Stieglitz. Alfred Stieglitz: The Key Set : the Alfred Stieglitz Collection of Photographs. Washington, D.C: National Gallery of Art, 2002. Pl 277, Pl 279
Homer, William I. Alfred Stieglitz and the American Avant-Guarde. Boston: New York Graphic Society, 1979. no. 8.
Rocha, Regina M, Paul Strand, and Helouise Costa. A Poética Fotográfica De Paul Strand. São Paulo, Brazil: Editora da Universidade de São Paulo, 2012. Fig. 28
Thornton, Gene. Masters of the Camera: Stieglitz, Steichen & Their Successors. New York: Ridge Press, 1976 p. 51
 unfortunately I cannot identify the source of this well written passage. If you know, please advise. Thank you.
Waldo Frank et al. (eds.), America & Alfred Stieglitz: A Collective Portrait, Doubleday, Doran & Company, Garden City, 1934, pl. XXV, B.
Dorothy Norman, Alfred Stieglitz: An American Seer, Random House/Aperture, New York, 1960, pl. X.
Doris Bry, Alfred Stieglitz: Photographer, Museum of Fine Arts, Boston, 1965, pl. 7.
John Walsh et al., In Focus: Alfred Stieglitz, Photographs from the J. Paul Getty Museum, The J. Paul Getty Museum, Malibu, pl. 4, p. 16.
Sarah Greenough & Juan Hamilton, Alfred Stieglitz: Photographs & Writings, Bulfinch Press/National Gallery of Art, Washington, D.C., 1999, pl. 15.
Sarah Greenough, Alfred Stieglitz: The Key Set, Volume One 1886-1922, Abrams/National Gallery of Art, Washington, D.C., 2002, pp. 164-66, cat. nos. 277-280.