148 NULLIUS IN VERBA j 



theory. And such a theory may become so all 

 embracing that it is called a law of nature. Those 

 great generalisations, the laws of gravity and the 

 laws of evolution, or the laws of chemical combina- 

 tion, have a beauty and dignity which appeal to 

 everyone. 



And on the practical rather than on the theo- 

 retical, side there is wonder, and to my mind beauty, 

 in the bigness and in the smallness of the spaces 

 that man can deal with. The astronomer measures 

 out his work, not by miles, but by the inconceivable 

 distance that light can travel in a year. The man 

 who studies bacteria measures by the micron, 

 25,000 of which go to the inch. To me there is 

 more fascination in the very small than in the other 

 extreme. It is wonderful to think that a plant — a 

 big tree for instance — is made up of countless 

 millions of cells, each of which was built by a 

 minute protoplasmic body, which Huxley has 

 compared to a delicate Ariel imprisoned like Shakes- 

 peare's sprite in an oak-tree. 



There is a dramatic effect in even the simplest 

 of experiments. I, for one, am never weary of the 

 time-honoured demonstration of a water-plant 

 giving off oxygen as it assimilates. A twig of 

 Elodea in a large beaker of water gives off no 

 bubbles in the dull Hght at the back of the room, 

 but when close to the window it does so. And with 

 proper precautions the rate of bubbling becomes an 

 accurate measure of the intensity of assimilation. 

 To complete the demonstration the experiment 

 should be repeated with water which has been 

 boiled, and therefore roughly freed from CO^, when 



