58 PART IL- SOME IMPORTANT METHODOLOGICAL TERMS. 



significant is concerned, he is almost exactly in the position of 

 a blind man in respect of colours. 



This is not astonishing when we ascertain how little is dis- 

 closed by ordinary experience. How is the uneducated man 

 to read the story of the stars, the earth, or the stratified rocks? 

 How is he to determine the depth of the strata or of the sea, 

 or the diameter of the earth or moon? How is he to follow 

 the system of mountain ranges; divine that volcanic regions 

 are situated close to the sea or to large lakes; or suspect the 

 existence or understand the cause of the trade winds? How 

 is he to surmise that the lump of flesh he is inspecting is a 

 muscle, and that buried in the lump are tendons, nerves, ar- 

 teries, veins, all held together by connective tissue ; or how is 

 he to determine the composition of the blood and its functions ; 

 or how is he to follow the processes of digestion and absorp- 

 tion of foodstuffs or the segmentation of the ovum? How is 

 he to decipher the history of mankind which stretches to the 

 tertiary period, and the complex signs of his own age? 



The information of what is remote in time and space is to 

 be acquired only by collective enquiries frequently lasting for 

 generations. Such facts defy conjecture, and much less is the 

 world of molecular masses open to his gaze, seeing that this 

 world is wholly screened from unaided sight and touch. The 

 weight of radium which may be detected experimentally by 

 means of the electrometer is 0,000,000,000,001 of a gram; the 

 quantity of xenon in the atmosphere is one part in 170,000,000; 

 there are said to be about 640 trillions of hydrogen molecules 

 in one milligram of the gas; the diameter of a molecule is 

 perhaps about 2X10~ 8 cms.; the number of molecules in 1 ccm. 

 of air under normal conditions is about 2?X10~ 19 ; a molecule 

 collides about 6,000,000,000 times a second; and the mass of 

 the electron is about ^th part of that of the hydrogen atom, the 

 weight of the latter being 1 . 63X10~ 24 gms. When it is considered 

 that scientific knowledge as in biology, chemistry, light, heat, 

 electricity, and magnetism is vitally contingent on an acquaint- 

 ance, however indirect, with substances invisible to the naked 

 eye or imperceptible altogether except indirectly, as with cer- 

 tain classes of bacteria, the impotence of common observation 

 becomes manifest. Hence we find that most scientific inquirers 

 seek by increased refinement of methods to pierce into the 

 world of the infinitesimal. Consequently, so far from desultory 

 observation suggesting to the man of science an extensive and 

 true hypothesis, he and hundreds of his confreres almost ex- 

 haust themselves in establishing a few comparatively narrow 

 generalisations grounded on an astounding number of obser- 

 vations witness, for example, the almost infinitely laborious 

 process of discovery of the numerous glandular secretions 

 which, at different stages, prepare the ingested food for ab- 



