264 K. YAMAGAWA 



with them, liowcver, I ]i:ul to reject them, and get n new stone-sphere 

 const rueted. 



The porjiliyritic stone-spheres of l^rofessors Ayrtoii and Perry 

 were found to increase in weiglit, if Icfr \n]i<j; enough in water, espe- 

 cially when water was hot. At first, it seemed natural to attrihute 

 this to soaking in throngli the surface*; and yet it was hard to believe 

 that soaking, and soaking only could explain such a great amount of 

 increase as 12 per cent, of weight, inasmuch as 12 per cent, in weight 

 was equivalent to some 30 per cent, in volume. Besides, the hole 

 in the sphere, which contained a thermoelectric junction, was always 

 found to be full of water — -a fact, hardly explicable by surface soaking. 

 Various devices were tried to prevent this supposed soaking, but 

 without any success. But when the balls were repolished, very fine 

 cracks were discovered. These cracks, of course, fidly explain the 

 increase of weight, and the presence of water in the hole. But ci'acked 

 balls, it was obvious, could not 1)0 used, and the construction of a new 

 ball was necessary. It is to be hoped, that the cracks did not exist at 

 the time when Professors Ayrton and I'eiTy experimented upon these 

 balls. 



A sphere of 10. 4() cm. in radius was cut out of a block of 

 saccharoidal marble (crystalline limestone, CaCOg) of density 2.71. A 

 small hole ß m. m. in diameter was bored into the sphere radially 

 towards the centre. Into this a nickel-iron junction enclosed in a 

 fine glass tube 4.2 m. m. in diameter was inserted. The jiuiclion 

 itself protruded out of the end of the glass tube so as to be in contact 

 with a drop of mercury at the centre of the sphere. The end of the 

 glass tulie wns completely closed by a cement ol' Japanese varnish 

 (uruslti), which at the same time fixed the glass and junction-wires. 



•Professors Ayrton and Perry seem to liint at this possiliility iu tlieir paper (see Phil. 

 Mag. 5th Series Vol. V. p 2r.7, last sentence of Section VII.1 



