Page:Popular Science Monthly Volume 86.djvu/108

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104
THE POPULAR SCIENCE MONTHLY

troleum. The plate was exposed for several hours, the image etched, and then prints were made as from an ordinary etching. The museum collection includes one of the first permanent photographs printed from a light etched plate by the heliographic process. This print is from Niepce's plate made-in 1824.

There are also several fine examples of Daguerre's work made in 1839 and later. His process, which came to be known as the Daguerreotype process, consisted of exposing a highly polished silvered copper plate, fumed with iodine, in a camera a few minutes, developing the exposed plate with mercury vapor and fixing the image with hypo-sulphite. This complex process involved five distinct operations; cleaning and polishing the plate, coating the plate with sensitive ioduret of silver, adjusting and exposing the plate in the camera obscura, developing the invisible picture after the exposure, and removing the sensitive coating so that no further ch: ge would take place in the picture. Daguerre and Niepce found that they were pursuing experiments of the same nature and went into partnership.

Six months prior to M. Daguerre's publications concerning his process, Mr. Fox Talbot communicated his photographic discoveries to the Royal Society, and afterwards issued an account of his scheme for preparing a sensitive paper for photographic reproduction which he called photogenic drawings. He prepared his paper by washing a sheet of fine writing paper with solutions of salt and silver nitrate. When dried this proved of use in securing prints of leaves, etc., in the camera obscura. Later he used iodide of potassium and other chemicals to perfect his system. Talbot's second process of paper making was patented in 1841, and was known as the calotype. The main advance in this system was the ability of the discoverer to make unlimited prints of his picture. Talbot obtained a third photographic patent on a process for photographing on unglazed porcelain, which a man by the name of Malone improved somewhat and eventually became associated with Mr. Talbot.

The museum collection, besides including many fine and unique examples of these first photographic processes, has much material on modern practical photography, including examples of different printing papers, and plates, stereoscopic pictures, flash-light paraphernalia, X-ray and colored photographs, astrophysical photographs and some early examples of moving picture making.

 

SCIENTIFIC ITEMS

We record with regret the death of Charles Sedgwick Minot, James Stillman professor of comparative anatomy in the Harvard Medical School, eminent for his contributions to embryology and biology and for public services 'n science; of Dr. Theodore Lipps, professor of psychology and philosophy of the University of Munich, and of Dr. Rudolf Emmerich, professor of hygiene and bacteriology in the University of Munich.

The Hayden gold medal of the Philadelphia Academy of National Sciences has been presented to Dr. Henry Fairfield Osborn, in recognition of his paleontological studies.—The De Morgan medal of the London Mathematical Society has been given to Sir Joseph Larmor in recognition of his researches in mathematical physics—One of the royal gold medals of the Royal Society, has been awarded to Professor Ernest Willliam Brown, of Yale University, in recognition of his investigations in mathematical astronomy

Dr. Allen J. McLaughlin, formerly of the Public Health Service, has assumed the duties of health commissioner of Massachusetts.—Dr. C.-E. A. Winslow has resigned from the College of the City of New York to become director of education in the reorganized State Department of Health.