Page:Popular Science Monthly Volume 86.djvu/107

Rh of Definition and Method in Psychology."

Vice-president Judson G. Wall, before the Section of Social and Economic Science: "Social and Economic Value of Industrial Museums."

Vice-president Theodore Hough, before the Section of Physiology and Experimental Medicine: "The Classification of Nervous Reactions."

Vice-president P. P. Claxton, before the Section of Education: "The American Rural School."

Vice-president L. H. Bailey, before the Section of Agriculture: "The Place of Research and Publicity in the forthcoming Country Life Development."

Perhaps the most notable event of the meeting will be the organization of the new section of agriculture, before which Vice-president L. H. Bailey will give the address noted above, and there will be a symposium on the field of rural economies. But each section will hold meetings of general interest.

As attractive as the programs will be the place of meeting. The buildings of the University of Pennsylvania afford admirable accommodations for all sections of the association and the separate societies, while in themselves affording much of interest to scientific visitors. Houston Hall, which was the first club house for students on a large scale to be established at a university, offers excellent headquarters, whore scientific men may meet and where committee meetings may be held. One or two of the societies will meet at the Academy of Natural Sciences, whose fine new building has recently been erected. From the time of Benjamin Franklin, Philadelphia and its institutions have been among the leading educational and scientific centers of the country. It was long our chief city for medical education and research, occupying somewhat the place in science that Boston filled in letters. The recent history of chemistry in America, by Dr. Edgar F. Smith, provost of the university and chairman of the local committee for the approaching meeting, indicates the city's leadership in that science. Other scientific

centers have overtaken Philadelphia, and the University of Pennsylvania has suffered from inadequate endowment. But in recent years the growth of the university has been remarkable, and, while it may be difficult for Philadelphia to rival New York and Washington, it will surely make contributions to science commensurate with its wealth and population

The history of photography is well illustrated by a series of cameras, plates, and prints exhibited in the U. S. National Museum. This collection of photographic apparatus and photographs, said to be the most complete in the world, has been collected and classified by Mr. T. W. Smillie, photographer of the museum for the past forty-five years. Work of nearly all the early inventors is to be seen, and what is said to be the first American camera, that made on Daguerre's specifications for Dr. S. F. B. Moore, in 1839.

The earliest camera, the camera obscura, used by Euclid in 300 B.C., was later improved upon by Bacon and others in the thirteenth century, and further improved by Porta in the sixteenth century. It is said that the action of light on fused silver chloride was used to make a photograph of the solar-spectrum by Scheele in 1777.

Unfortunately there was then no method known for fixing the prints, and in consequence only imitations of this method are to be seen in the museum collection. Thomas Wedgwood experimented along this same line in 3 802, and prepared a paper on the subject.

The first successful inquirer to secure permanent pictures through the influence of the sun 's rays, seems to have been Nicephore Niepce, who in 1824 effected the process of heliography by the use of a varnish made of asphaltum, or bitumen of Judea, applied to a highly polished metal plate or a glass plate, and developed by essential oil of lavender and white