C. Hunter and E. M. Rich 
4 6 
the stem elongates the platinum electrode E is raised the corresponding 
height. The spherometer is adjusted so that contact is just made 
between its central point and E —this is indicated by the deflection 
of the needle of the galvanometer owing to the completion of the 
circuit. The reading of the spherometer and the time are noted. The 
circuit is then broken by withdrawing the centre point of the sphero¬ 
meter a fraction of a millimetre—this distance is duly recorded, 
observation kept on the galvanometer and the time noted when the 
circuit is completed again owing to the raising of the electrode due 
to the growth of the stem. The operation is then repeated and thus 
the rate of growth of the stem can be accurately determined. 
The spherometer employed was graded into 0*005 mm - units, but 
even smaller distances than these might be measured by suitable 
vernier attachments. Corrections due to the interfering effects of 
fluctuations in temperature on the metal supports and on the glass 
