SECTION 22 OBSERVATION. 317 



CONCLUSION 23. 



Need of Exhausting Classes of Facts, their Conditions, and the 

 Uniformities accompanying them. 



157. (A) EXHAUSTING CLASSES OF FACTS.-ln his 

 famous example of the investigation of heat, Bacon plainly 

 implies that classes of facts should be exhausted where prac- 

 ticable, and in connection with the problem of effective obser- 

 vation scientific methodology demands that the enquiry should 

 proceed till no new classes of relevant and material facts can 

 be found. With Prof. Karl Pearson we should cease to look, 

 initially, for one principal factor only, and examine all possible 

 factors, and with Prof. Schuster we should inspect all possible 

 freouencies. 



158. (B) EXHAUSTING CONDITIONS. The conditions 

 should be also exhausted. We should endeavour to examine 

 all the conditions that we can possibly discover or utilise, and 

 we need to be searching for new classes of conditions long 

 after the first or second success or failure to discover any. 



159. (C) ACCOMPANYING UNIFORMITIES We should 

 ceaselessly aim at ascertaining accompanying uniformities. That 

 earthquakes proceed along earth fissures and are specially 

 common and disastrous along ocean borders, mountain districts, 

 and around active volcanoes; that volcanoes are mostly situated 

 near the sea; that the daily retardation in the tides approxi- 

 mately equals the daily retardation of the moon, and that the 

 height of the tides locally is determined by sundry local factors; 

 that the configuration of a district regulates to some extent 

 the rainfall, and that its configuration is frequently determined 

 by its water courses; that day and night are caused respec- 

 tively by the presence or the absence of the sun; that the bisons 

 and other hoofed animals are, perhaps, related as cause and 

 effect to the treeless spaces which they haunt; that the preva- 

 lence of rats coincides with the occurrence of certain epidemics, 

 and that a certain relation obtains between stagnant pools and 

 mosquitoes, on the one hand, and open dustbins and houseflies, 

 on the other; that those addicted to alcohol have less power 

 of resistance to disease; that relatively moderate but moist 

 heats are far more oppressive than those of hotter but drier 

 localities; that the exceeding dryness of hot desert climates 

 causes the air to be hotter during the day and colder during 

 the night, as compared with more humid climates; that "the 

 presence of trees reduces the temperature of the atmosphere, 

 whilst radiation is hindered at night, that trees thus produce 

 the effect of equalising temperature, and, by keeping the atmo- 

 sphere moist, they induce the fall of rain"; that the physical 

 features of a district or a country (e.g., the presence of ex- 

 tensive coal measures) determine in no small degree its social 

 features; or that home education reacts on school education 



