154 LIFE AND WORK OF SIR JAGADIS C. ROSE 



times or so. Even here several hours must elapse before 

 growth becomes perceptible ; but during this long period 

 the external conditions such as light and warmth can 

 hardly but change, thus confusing, if not even vitiating, 

 the results. 



The external conditions can be kept constant only for 

 a few minutes ; and it is therefore necessary to obtain 

 growth-magnification to something like ten thousand 

 times. The difficulty of obtaining such magnification is 

 *so great that it took Bose about eight years to overcome 

 it, and his ' High Magnification Crescograph ' (Fig. 17) 

 may be regarded as a veritable triumph in invention. The 

 apparatus not only produces this enormous magnification, 

 but also automatically records the rate of growth and its 

 changes, in a period as short as a minute. 



Bose employs for the purpose a compound system of 

 two levers ; the first magnifies a hundred times, and the 

 second enlarges the first a hundredfold, the total magnifi- 

 cation being thus 10,000 times. But the double system 

 of levers introduces difficulty on account of their weight ; 

 this was surmounted by the employment of an alloy of 

 aluminium, which combines great rigidity with excep- 

 tional lightness. The friction at the bearings increased by 

 the deposit of invisible dust particles introduced a further 

 difficulty ; bearings even made of ruby did not obviate 

 the trouble. Bose was finally able to devise a new form of 

 suspension by which all difficulties were fully overcome. 



These high magnification records show that growth is 

 often not steady and continuous, but proceeds in rhythmic 

 pulses. In normal Calcutta conditions these average 

 about three per minute. Each pulse exhibits a rapid 

 uplift, and then a slower and partial recoil, amounting to 

 a recession of about a fourth of the distance at first gained ; 

 and from the resultant progress it starts for its next rise. 

 Our mental image of the growth-process is thus transformed 

 by these tracings from a steady mechanical progress to 

 that of the wavelets of a rising tide. Still, there are also 



