ON THE STUDY OF PHYSICS. 283 



out from the centre and travel in the other direction. 

 If the guess be true, certain consequences must follow 

 from it, and we appeal to the law and testimony of 

 experiment whether the thing is so. Thus is the 

 circuit of thought completed, from without inward, 

 from multiplicity to unity, and from within outward, 

 from unity to multiplicity. In thus traversing both 

 ways the line between cause and effect, all our reason- 

 ing powers are called into play. The mental effort 

 involved in these processes may be compared to those 

 exercises of the body which invoke the co-operation of 

 every muscle, and thus confer upon the whole frame the 

 benefits of healthy action. 



The first experiment a child makes is a physical 

 experiment : the suction-pump is but an imitation of 

 the first act of every new-born infant. Nor do I think 

 it calculated to lessen that infant's reverence, or to 

 make him a worse citizen, when his riper experience 

 shows him that the atmosphere was his helper in ex- 

 tracting the first draught from his mother's breast. 

 The child grows, but is still an experimenter : he grasps 

 at the moon, and his failure teaches him to respect 

 distance. At length his little fingers acquire sufficient 

 mechanical tact to lay hold of a spoon. He thrusts 

 the instrument into his mouth, hurts his gums, and 

 thus learns the impenetrability of matter. He lets the 

 spoon fall, and jumps with delight to hear it rattle 

 against the table. The experiment made by accident 

 is repeated with intention, and thus the young student 

 receives his first lessons upon sound and gravitation. 

 There are pains and penalties, however, in the path of 

 the enquirer : he is sure to go wrong, and Nature is 

 just as sure to inform him of the fact. He falls down-- 

 stairs, burns his fingers, cuts his hand scalds his tongue, 

 and in this way learns the conditions of his physical 



