BRIEF HISTORICAL SUMMARY 



In dealing with the historical development of projection three forms of 

 apparatus must be considered: 



I. NATURAL CAMERA OBSCURA 



The formation of images in a dark place, the light from the brilliantly illum- 

 inated objects or scenes being admitted through a small opening, is a perfectly 

 natural phenomenon and entirely independent of man's invention or control. 

 This is represented by images of the sky with its clouds and the brilliant scenes 

 of nature pictured on the walls of caves facing the scenes, and the images of 

 the sun admitted through chinks between the leaves, etc. 



In rooms of man's construction such images are often seen if light enters 

 through a chance hole in the right position. General Waterhouse, from his 

 own observation, says it is a common occurrence in the bungalows of India, 

 and the writers have often seen the same in America. 



*It was our intention when this work was undertaken to include a somewhat 

 extended account of the discoveries and inventions relating to vision, including 

 spectacles, general optics, and optical instruments, especially the telescope, the 

 microscope and projection apparatus of all kinds. As the book has already 

 exceeded its limit in size, this extended account must wait for a special work. 

 We have thought it best, however, to add a brief summary of the more per- 

 tinent points, and a historical bibliography which will put those interested on 

 track of the special and early sources of information. 



Our appreciation is great for the aid we have received from many sources. 

 First of all to the Library of Cornell University for its magnificent collection 

 of works bearing on the history of science, for the purchase of rare and costly 

 works, and for the trouble taken to borrow from other libraries, rare works for 

 our use. Among the other libraries drawn upon we mention in the first place 

 that of the Surgeon General's Office in Washington, D. C. Those of Columbia, 

 Chicago, Harvard and the University of Pennsylvania also loaned us many 

 works. 



Among the individuals who gave us special aid are: 



Professor George L. Burr, for securing the portrait of Scheiner, (fig. 407). 



Professor E. Lavasseur of the College of France who supplied the photograph 

 for the portrait of Marey (fig. 412). 



Mr. Augustus J. Loos of Philadelphia for securing information concerning 

 the Langenheim brothers who were the first to make photographic lantern 

 slides by the albumen process (1850). 



Mr. Edward Pennock of Philadelphia for putting us in communication with 

 Mr. C. W. Briggs of that city. Mr. Briggs gave us much valuable information 

 concerning his father, Dr. Daniel H. Briggs, who made the first photographic 

 lantern slides by the collodion process (1851-1852). 



Effie Alberta Read, Ph.D., M.D., for looking up references and verifying 

 quotations in the libraries of Washington, D. C. 



Theodore Stanton for aid in securing the photograph of Marey, (fig. 412). 



And finally to Dr. A. C. White of the Cornell University Library for transla- 

 tions from the Greek and Latin works of the old writers, in which some of the 

 earliest information on our subject is to be found. 



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