400 Messrs. Kei Iokibe and Sukeaki Sakai: Effect of 



(2) The internal viscosity of a wire is enormously reduced 

 by annealing. 



(3) The internal viscosity of an annealed wire gradually 

 decreases by suspending a weight at its lower end and 

 leaving it to itself. A continuous oscillation also produces 

 the same effect. 



(4) The logarithmic decrement considerably increases 

 with the amplitude o£ oscillation. This increase is generally 

 greater, the higher the temperature of the wire. 



Thus, all the experiments, except one, were limited to 

 temperatures below 300° C, but the results obtained were so 

 interesting and promising, both from the theoretical and 

 practical points of view, that we determined to repeat the 

 same investigation and also to extend the range of tempera- 

 ture to the highest possible. 



2. Arrangements and Method of Experiments. 



The method of experiment consists in measuring the period 

 and the logarithmic decrement of torsional oscillation of a 

 test-wire carrying a weight. The arrangement is sketched 

 in fig. A. S is a test-wire 0*6 to 0*7 mm. thick and 25 cm. 

 long, and carefully annealed at a proper temperature. PP 

 are two thick porcelain rods, to which both ends of the wire 

 are firmly clamped by means of short steel pieces. These 

 porcelain tubes prevent the loss of heat in the wire outward 

 through conduction, and hence the temperature of the wire 

 can be made uniform throughout its whole length. BB are 

 two brass rods rigidly connected with the porcelain rods, as 

 shown in the figure ; the upper rod is firmly clamped by a 

 screw c to the tripod stand E, resting on a stout support G. 

 At the middle portion of the lower brass rod a concave 

 mirror M is mounted ; by means of this mirror a vertical 

 wire, illuminated from behind by a lamp, forms a sharp 

 image on a distant scale. The distance between the mirror 

 and the scale is 2 metres. H is a thin circular disk made of 

 brass on which a flat lead ring is co-axially placed. Two 

 lead rings of different masses were made, the lighter one of 



O 7 O 



which was used in the case of soft metals and the heavier in 

 the case of hard ones. ^ is a needle fixed to the brass rod 

 B ; this needle is used when a torsional oscillation is to be 

 given to the suspended system. K is a holder with an axial 

 hole small enough to receive the needle within it loosely. 

 To obtain a torsional oscillation, the holder is raised by a 

 rack and pinion to receive the needle in its narrow hole, and 

 the oscillation is excited by means of air-puffs through lead 



