158 LIFE AND WORK OF SIR JAGAD1S C. BOSE 



in the rate of growth. No satisfactory explanation of these 

 movements has been forthcoming, since the apparatus 

 in use was too crude 'to detect the variation of growth- 

 rate, which was itself very minute. But with the High 

 Magnification Crescograph, Bose succeeded in obtaining 

 tracings which measured the rate of growth as small as 

 nnsVjnr i nc h P er second. He was thereby able to record 

 changes induced in normal growth by the action of various 

 agents, by contact, by variation of temperature, by radiant 

 heat and light, by the stimulus of gravity, by electrical 

 currents, and by various chemical agents. From these 

 fundamental reactions he was able, as we shall see later, 

 to offer a complete explanation of the diverse movements 

 in plants. 



After observing in the laboratory the extraordinary 

 sensitiveness of this Crescograph with its magnification of 

 ten thousand times, the writer offered the opinion that 

 surely the utmost perfection had at last been reached ; 

 but to this Bose made the naive and cryptic rejoinder that 

 ' man is never satisfied ' ; and forthwith began to push on 

 his investigations towards obtaining still higher magnifica- 

 tion. He at first tried increasing his system of levers from 

 two to three. But he soon found that, though theoretically 

 possible, a limit to magnification is imposed on account 

 of additional weight, and friction at the linking of one lever 

 to another. He therefore thought of a weightless lever, 

 and of linking without material contact. This he succeeded 

 in effecting by the invention of his Magnetic Crescograph 

 (Fig. 18) ; here the movement of the lever of his ordinary 

 Crescograph upsets a very delicately balanced magnetic 

 system. The indicator is a reflected spot of light from a 

 mirror carried by the deflected magnet. In this way Bose 

 obtained a range of magnification from one to a hundred 

 million times. 



Our mind cannot grasp magnification so stupendous. We 

 can, however, obtain some concrete idea of it by finding what the 



