15 EXPERIMENTS ON 



of the hygrometers, consulted in the preceding expe- 

 riments on refraction. 



The Panimooloo grass, wliich grows chiefly on 

 mountains, and is well known to the natives, from 

 its beards easily catching and adhering to their 

 clothes, produces a kind of ear, somewhat resembhng 

 that of wheat. Its seed vessels shoot out long fibres, 

 of a hardy texture, which entwist one with the 

 other from left to right, so as to resemble, when in 

 that state, a diminutive coir rope. 



These fibres, or beards, are the part of the plant 

 used in the construction of the hygrometers, and 

 consequently deserve particular notice. 



Each fibre shoots out, in a straight line, nearly to 

 the length of an inch, from the seed vessel to which 

 it adheres ; then tapers off, in curls, to a very fine 

 end, so that the former part of it can alone be used 

 for the present purpose. 



When viewed through a magnifying glass, it appears 

 to be made up, like a rope, in broad strands, twisted 

 from left to right ; which, when water is applied 

 (contrary to its effect on a rope) are gradually unfold- 

 ed, and cause the motion of which I availed myself. 



Tlie twists, in the straight part of the stem, are 

 from 5 to 7 in number ; and these, as I have found 

 by experiments, nearly mark the number of revolu- 

 tions, of which the fibre is susceptible, by the appli- 

 cation of moisture. 



When dissected, the stem was found to be made up 

 of two fibres, connected by a slight membrane, easily 

 divided, and twisted round each other, until they 

 were united in a common stalk, at the seed vessel at 

 one end,, and above the first curl at the other. 



