390 MR. C. O^NEILL ON AN APPARATUS 



fixed for holding the substance to be tested. D is a fixed 

 support, provided with means of attaching the fibre to be 

 tested. F is a lever with a long and short arm ; and G is a 

 graduated scale, over which the point of the long arm of 

 the lever moves. H is a table or support upon which the 

 apparatus rests ; and E is a measuring-flask or bottle which 

 serves to ascertain the amount of water drawn off" from A. 



To use the apparatus, it is nearly filled with water, and 

 the fibre, thread, or wire to be tested is' secured to the 

 fastenings on B and D in a slack state ; water is drawn off 

 from the cock C until the fibre, &c., is taut, or until the 

 long arm of the lever ceases to move over the scale. The 

 measuring- or weighing-flask is then put under the cock, 

 and the water allowed to flow into it in a regular stream, 

 with the hand upon the tap, until the fibre breaks, when 

 the cock is instantly turned ; the quantity of water is then 

 ascertained, and from it the amount of strain upon the 

 fibre or thread at the moment of rupture. The move- 

 ments of the long arm of the lever are watched during the 

 operation, and noted at the moment of breaking ; this 

 gives the stretch of the fibre or thread, and serves to cor- 

 rect the indications given by the water-fiask. To prevent 

 damage to the apparatus by the falling of the cylinder 

 upon the breaking of the thread, a stop, not represented in 

 the sketch, is fixed, which only allows a short fall of half 

 an inch or so. 



The principle of the apparatus is so simple, that it 

 hardly requires any explanation. At the beginning of the 

 operation the tube is supported by the water, and there is 

 no weight upon the fibre; by drawing off the water the 

 support is gently removed, and the weight of the cylinder 

 gradually thrown upon the fibre or thread. 



The weight thrown upon the fibre is in relation to the 

 weight or volume of water drawn off; but the ratio be- 

 tween these quantities will vary for every different dimen- 



