Page:Popular Science Monthly Volume 13.djvu/129

Rh The Sugar-Beet in North Carolina. By A. Ledoux. Raleigh: Farmer and Mechanic print. Pp. 50.

The Salt-eating Habit. By R. T. Coburn. Dansville, N. Y.: Austin, Jackson & Co. print. Pp. 29.

The Star-Finder, or Planisphere, with Movable Horizon. New York: Van Nostrand.



The Growth of Photography.—At one of the public lectures recently given under the auspices of the New York Academy of Sciences, Prof. Charles F. Chandler sketched the progress of photography during the last hundred years. The first authentic record of pictures made by solar agency he finds in Cooper's "Rational Recreations," published in 1774, where an account is given of the marking of bottles by silver salts. Next came Scheele's experiments on the effect of exposing to light paper sensitized by the same salts. The first genuine sun-pictures were probably produced by Bolton and Watt, who were followed by Humphry Davy and Wedgwood. Still, down to the beginning of the second quarter of the nineteenth century, photography had not advanced beyond the stage of producing images of plant-leaves laid on sensitized paper, and exposed to light. These images, crude as they were, soon disappeared on continued exposure of the paper to the light, for as yet no means of fixing the photograph image had been discovered. Niepcé studied the subject experimentally for nearly fifteen years, without any very encouraging results, but in 1824 he associated with himself Daguerre, who in 1839 announced to the world his discovery of a method of producing permanent sun-pictures. Dr. Draper, of New York, added sundry important improvements to Daguerre's method. Fox-Talbot produced the first silvered-paper photograph, which was the germ of the modern sun-picture. The great development came in 1841, when Schönbein discovered gun-cotton. Cotton, he found, when exposed to nitric acid, becomes explosive, and soluble in a mixture of alcohol and ether. The discovery of this latter property was the foundation of the common photographic process, where a film of collodion, sensitized by silver iodide, produces the "negative" image, from which thousands of pictures may be struck off. It was stated by Prof. Chandler that Albert, a photographer of Munich, and Edward Bierstadt, of New York, are engaged in perfecting a process for printing photographs in colors.

The Development of Botanical Science.—The progressive development of botanical science is forcibly exhibited by the Belgique Horticole, in a numerical statement of the different species of plants named in sundry ancient documents, and now ascertained by botanists. Thus, in the Bible, we are told, about fifty plants are clearly determined, while about as many more are mentioned in more general terms. Hippocrates mentions 234 species, Theophrastus about 500, Dioscorides over 600, and Pliny 800. In the sixteenth century Conrad Gerner names 800, Charles de l'Escluse 1,400, Dalechamps 2,731, and Gaspard Bauhin 6,000. In 1694 Tournefort describes 10,146 species. He was the first to class the species of plants into genera, of which he reckoned 694. In the eighteenth century Linné defined 7,294 plants, distributed in 1,239 genera. In 1805 Persoon's "Synopsis Plantarum" included nearly 26,000 species, and in P. de Candolle's "Elementary Theory of Botany" 30,000 species are said to be known scientifically. Stendel's "Nomenclator Botanicus" (published in 1824) contains 78,000 names of plants. Loudon's "Hortus Britannicus" (1839) enumerates 31,731 species in 3,732 genera. According to Endlicher (1840), there were 6,895 known genera in the vegetal kingdom, which number is increased to 8,931 by Lindley in the year 1853. In 1863 Bentley estimated the known species at 125,000. The Belgique Horticole thus classes the species now known:

or, in all, about 120,000 species distributed among 8,000 genera. The species actually cultivated number 40,000, and these are true botanical species, not simply races or varieties.

Facts about the So-called "Rain-Tree."—For some months there has been circulating in the newspapers a notice of a tree 