Page:Popular Science Monthly Volume 86.djvu/108

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I04

��THE POPULAR SCIENCE MONTHLY

��troleum. The plate was exposed for several hours, the image etched, and then prints were made as from an ordi- nary etching. The museum colleetiou 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 ]824.

There are also several fine examples of Daguerre's work made in 1839 and later. His process, •vhich came to be known as the Daguerren^ype process, consisted of exposing a highly polished silvered copper plate, fumed with io- dine, in a camera a few minutes, de- veloping the exposed plate with mer- C'lry vapor and fixing the image with liypo-snlphite. This complex "process 'nvolved five distinct operations; clean- ing and polishing the plate, coating the plate with sensitive ioduret of silver, adiusting and exposing the plate m the camera cbscura, developing the in- visible picture after the exposure, and removing the -n sitive coating so that no further ch: ge would take place in the picture. Daguerre and Niepce found that they were pursuing experi- ments of the same nature and went into partnership.

Six months prior to M. Daguerre's publications concerning his process, Mr. Fox Talbot communicated his photo- graphic discoveries to the Eoyal So- ciety, and afterwards issued an ac- count of his scheme for preparing a sensitive paper for photographic re- production 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 secur- ing prints of leaves, etc., in the camera obscura.. Later he used iodide of po- tassium 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 un- limited prints of his picture. Talbot obtained a third photographic patent

��on a process for photographing on un- glazed porcelain, which a man by the name of Alalone improved somewhat and eventually became associated with Mr. Talbot.

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

SCIENTIFIC ITEMS

We record with regret the death of Charles Sedgwick Minot, James Still- man 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, pro- fessor 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 Phila- delphia Academy of National Sciences has been presented to Dr. Henry Fair- field Osborn, in recognition of his pale- ontological studies. — The De Morgan medal of the LfOndon Mathematical So- ciety has been given to Sir Joseph Larmor in recognition of his re- searches in mathematical physics — One of the royal gold medals of the Eoyal Society, has been awarded to Professor Ernest Willliam Brown, of Yale Uni- versity, in recognition of his investiga- tions in mathematical astronomy

Dr. Allen J. McLaughlin, formerly of the Public Health Service, has as- sumed the duties of health commis- sioner of Massachusetts. — Dr. C.-E. A. Winslow has resigned from the College of the City of New York to become di- rector of education in the reorganized State Department of Health.

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