55 



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. 



i 



The three circumstances, under which this exceptional increase of 



the teredo was observed, were a mod- 

 erate 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 tempera- 

 ture. 



IV. 



Experiments in the Preserva- 

 tion of Wood from the Attacks 

 of the Teredo. To justly appre- 

 ciate 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 be- 

 ing done to our marine works by the 

 teredo, very many methods of pres- 

 ervation were recommended on all 

 sides to the Government, and that 

 the nature of many of these remedies 

 was kept secret by the persons extol- 

 ling them. In order that its labors 

 should offer every guarantee of im- 

 partiality, 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. 



Fig. 14. This cut was made from a Teredo 

 navalis, taken from a pile exposed two 

 seasons (1876 and 1877) at Horn Island, 

 Gult of Mexico. When first taken from 

 the wood it was eighteen inches long. 



