174 THE POPULAR SCIENCE MONTHLY. 



The senses, indeed, are not formed to enable man to solve the prob- 

 lems of Nature, but, as with the lower animals, merely to make exist- 

 ence possible, and, in a limited and incidental way, agreeable. And yet 

 it is through these feeble senses that all human knowledge enters the 

 brain, since all deductive reasoning must be based on previous inductive 

 observation. More humiliating still, and more instructive in its rela- 

 tions to human testimony, is the lack of precision and power of appre- 

 ciating details at long distances through the eye. At the interval of 

 half a mile we are unable to recognize the countenance of our dearest 

 friend ; while ordinary type, in order to be read, must be held within a 

 few inches of the face. 



A recognition of the limitations of the sight the king of the senses 

 makes the recognition of the limitation of the inferior faculties of 

 hearing, smelling, tasting, and touching, easy and inevitable. Vibra- 

 tions of the air below 32 per second, or above 100,000 per second, at the 

 extreme, make no impression on the human ear ; and, as experiments 

 in the presence of audiences have proved, sensitive flames may react to 

 atmospheric vibrations in perfect silence. Ordinary conversation is 

 audible only within a few feet, while powerful-voiced orators in their 

 mightiest efforts reach but a few thousands of people. The sense of 

 smell is so restricted in its capacity that it fails to detect many of the 

 most deadly poisons and causes of epidemics, and is of such slight 

 practical service to man that patients who, through disease, have lost it 

 entirely, sometimes say that they would not care to have it restored. 



The sense of touch, of which all the other senses are supposed to be 

 modifications, being of necessitj' limited to actual contact, is of no value 

 in the study of anything at a distance. 



It is clear, therefore, that the senses open but a few rooms in the 

 infinite palace of Nature, and of these few they give us but feeble and 

 imperfect glimpses. Throwing all questions of supernaturalism aside, 

 it must be allowed that the senses bring us into direct relation with 

 only an infinitesimal fraction of the natural ; we are practically shut 

 out of a knowledge of Nature, of which we are a part ; hence the nar- 

 row limitations of human knowledge, all of which must be inductively 

 based on what the senses are able to teach us, although the super- 

 structure may by deduction be raised very high. The elementary and 

 all-important facts in Nature are precisely those of which the senses, 

 singly or combined, give us little information, or none whatever. The 

 great forces light, heat, electricity, gravity can be studied in their 

 effects only, not in themselves in what they do rather than in what 

 they are ; hence it is that the great and central advances in science 

 the Copernican theory, the theory of gravitation, the wave-theory of 

 light are along the line of deductive, not inductive, investigation. If 

 we depended on induction, we should know nothing of Nature, but 

 would be blind babes wandering in a pathless forest. The first step in 

 the evolution of any great science has ever been and must ever be the 



