Page:Popular Science Monthly Volume 13.djvu/568

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THE POPULAR SCIENCE MONTHLY.

from a diminution in the quantity of the rainfall; the same opinion is found expressed in the reports of many chief engineers of Waterstaat. To decide whether this opinion was well founded, careful analyses were made in 1859, which, compared with those made at other epochs, showed that the proportion of salts found in the water of the Y was just double what it was in 1855, and a third more than in 1825.

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The three circumstances, under which this exceptional increase of PSM V13 D568 Teredo navalis.jpgFig. 14.—This cut was made from a Teredo navalis, taken from a pile exposed two seasons (1876 and 1877) at Horn Island, Gulf of Mexico. When first taken from the wood it was eighteen inches long. the teredo was observed, were a moderate rainfall, and, as a direct or remote consequence, a falling of the level of the rivers, and an increase of the saltness of the water of our arms of the sea. As an additional favoring circumstance should also be noted an increase in the temperature.

 
IV.

Experiments in the Preservation of Wood from the Attacks of the Teredo.—To justly appreciate the experiments tried by the commission, it must be borne in mind that when it was discovered, in 1858 and 1859, that great injury was being done to our marine works by the teredo, very many methods of preservation were recommended on all sides to the Government, and that the nature of many of these remedies was kept secret by the persons extolling them. In order that its labors should offer every guarantee of impartiality, and although convinced in advance of the inefficacy of a large number of the means proposed, the commission decided not to lay aside any without a trial. Moreover, as far as possible, it had the pieces of wood to be experimented with prepared by the inventors or proposers of the processes, in order to protect itself from every accusation of unfairness.

The experiments were made the first year in the ports of Flessingue,

  1. Several pages omitted, of no especial interest to American readers, describing local observations of the state of the water and atmosphere, and analyses of the waters, to show their chemical character.