SCIENTIFIC METHOD 81 



ing nature of phenomena can give science advantage 

 over chance in hitting upon useful discoveries and 

 inventions. It is, therefore, natural to find him ap- 

 plying his method of induction his special method 

 of true induction to the investigation of heat. 



In the first place, let there be mustered, without 

 premature speculation, all the instances in which 

 heat is manifested flame, lightning, sun's rays, 

 quicklime sprinkled with water, damp hay, animal 

 heat, hot liquids, bodies subjected to friction. Add 

 to these, instances in which heat seems to be absent, 

 as moon's rays, sun's rays on mountains, oblique rays 

 in the polar circle. Try the experiment of concen- 

 trating on a thermoscope, by means of a burning- 

 glass, the moon's rays. Try with the burning-glass 

 to concentrate heat from hot iron, from common 

 flame, from boiling water. Try a concave glass with 

 the sun's rays to see whether a diminution of heat 

 results. Then make record of other instances, in 

 which heat is found in varying degrees. For exam- 

 ple, an anvil grows hot under the hammer. A thin 

 plate of metal under continuous blows might grow 

 red like ignited iron. Let this be tried as an experi- 

 ment. 



After the presentation of these instances induction 

 itself must be set to work to find out what factor is 

 ever present in the positive instances, what factor 

 is ever wanting in the negative instances, what fac- 

 tor always varies in the instances which show varia- 

 tion. According to Bacon it is in the process of 

 exclusion that the foundations of true induction are 

 laid. We can be certain, for example, that the 

 essential nature of heat does not consist in light and 



