TWENTY-FIFTH CONGRESS, 1837-39. 179 



textile fibres have, if possible, been less clearly understood 

 than the peculiar properties of the cordage itself. Thus 

 the name " sea grass " is sometimes applied to the fibres of 

 a fleshy perennial plant of the agave genus, which grows 

 on dry rocky hills far in the interior of the country. The 

 influence of heat and moisture on all the diflerent materials 

 employed for either cordage, sails, hammocks, bags, or cloth- 

 ing, presents a wide field for useful research. The relative 

 strength and durability of tarred and white cordage has 

 already engaged attention in Europe, but further inquiries 

 spring up as new materials are introduced. 



Not less important than either of the preceding topics is 

 that of the strength and other properties of iron, as appli- 

 cable to the fabrication of chain cables and smaller chains 

 for standing or running rigging, (the latter particularly for 

 steam vessels,) and of bolts and anchors for all the various 

 sea and river craft. jSTot only the strength and elasticity, 

 but the chemical purity also of this material, and its power 

 to resist corrosion, are objects of deep interest. 



The naval and commercial marine interests are alike in- 

 volved in an inquiry into the possibility of obtaining an 

 economical substitute for copper for the sheathing of ves- 

 sels ; and whether that material itself may yet be defended 

 from the corrosion which now causes so heavy a charge on 

 the Government, as well as on the private shipowner. A 

 movable galvanic armature has been suggested for this 

 purpose, but awaits a trial of its eflicacy. 



Other sjibjects of inquiry likewise press upon the atten- 

 tion, such as the most efficient and economical forms of 

 pumps, and the best methods of working them ; the best 

 modes of heating, ventilating, and disinfecting vessels at 

 sea, and of freeing them from vermin ; of preserving every 

 species of provision on long voyages ; the practicability of 

 obtaining fresh water by any convenient apparatus for dis- 

 tillation on shipboard ; and the most eftective means of 

 securing ships from electrical discharges. Time would fail 

 us to enumerate all the beneficial results of an enlightened 

 application of science to the operations of dock yards, to 

 the construction and use of dry docks, screw docks, floating 

 docks, and marine railways. 



To show that the importance of science to the naval 

 interest is not herein overrated, it may not be amiss to 

 mention, that a single division of science applicable to this 

 service of naval construction, that of the influence of form 

 on the flotation and motion of solid bodies in liquids, has 

 not been thought unworthy to occupy the attention of some 



