20 CHAP. II. HIGH MAGNIFICATION CRESCOGRAPH 



the deflected system a further magnification of 20,000 times, 

 the total magnification being thus a millionfold. This 

 was verified by moving the short arm of the lever through 

 0-005 mm., by means of a micrometer screw. The resulting 

 deflection of the spot of light at a distance of 4 metres was 

 then found to be 5000 mm. or a total magnification of 

 a million times. With a more sensitive apparatus the 

 magnification was increased even to 50 million times. ^ 



A concrete idea of this order of magnification is formed 

 when it is realised that this is 30,000 times greater than 

 that produced by the highest powers of the microscope. 

 With such a magnification a single wave of sodium light 

 would appear lengthened to about 3000 cm. 



Demonstration by Magnetic Crescograph 



With this apparatus I have been able to give striking 

 demonstrations of various phenomena of growth before 

 large audiences at different scientific centres. Employing 

 even the slowly growing flower-bud of the Crinum Lily (the 

 average rate of growth of which is only 0-0006 mm. per 

 sec), a magnification of a million times was found to be 

 m.ore than ample. The excursion of the indicating spot 

 of light exhibiting the movement of growth was found to 

 be 300 cm. in 5 seconds, the scale being placed at a distance 

 of 4 metres. The temperature of the room was 30° C 



Experiment 6. — The plant-chamber was then cooled 

 to 26° C. by the blowing in of cool water-vapour. The time 

 taken by the spot of light to traverse the 300 cm. length of 

 the scale was now 20 seconds, the growth-rate being thus 

 depressed to one-fourth. Under continuous lowering of 

 temperature, the rate was slowed down till there was arrest 

 at 21° C. Warm vapour was next introduced which 

 gradually raised the temperature of the chamber to 35° C. 

 The spot of light now rushed across the scale in a second 

 and a half, that is to say, growth was enhanced to more 



^ Plant Autographs (1927), p. 95. 



