K. HONDA. T. TERADA, Y. YORHIDA, AND D. ISITANI. 



Fig. 



pen on tlie vortical cylinder revolving uniformly. Tlie whole 

 apparatus, which is constructed in a form specially adapted for 

 transporting and setting, is given in tlie photograph No. 3 and 

 4 of the frontispiece. 



The relation between the cliange of water level above the 

 jar and the mercury meniscus in the tube can be found in the 

 following way : — 



Let /^ h, (Fig. 5.) 

 be the levels of sea 

 water above and inside 

 the jar respectively ; 

 //., //g be the levels of 

 mercury in the tubes 

 B and C. Let /; be 

 the common height of 

 the mercury in the two 

 tubes, when the jar is 

 not immersed in water. If tt and P be the pressure of atmosphere 

 and the pressure within the jar respectively, we have 



where p is the the density of mercury. 



If Sj, a be tlie cross section and the height of tlie jar, and 

 s,„ s,^ the cross section of the tubes B and C respectively, we 

 have, by assuming Boyle's law, 



r \ .<?i(« — Aj) + 1; -f s.,{b - lu) \ = const., 



where r is the volume of the copper tube plus tliat of tlie 

 part of the tube B lying above the level h. 



The differentials of the above two equations are 



