216 FRAGMENTS OF SCIENCE. 



while the latter is Physics applied to atoms and molecules. 

 The subjects of Physics proper are therefore those which 

 lie nearest to human perception: light and heat, color, 

 sound, motion, the loadstone, electrical attractions and 

 repulsions, thunder and lightning, rain, snow, dew, and so 

 forth. Our senses stand between these phenomena and the 

 reasoning mind. We observe the fact, but are not satisfied 

 with the mere act of observation: the fact must be 

 accounted for fitted into its position in the line of cause 

 and effect. Taking our facts from Nature we transfer 

 them to the domain of thought: look at them, compare 

 them, observe their mutual relations and connections, and 

 bringing them ever clearer before the mental eye, finally 

 alight upon the cause which unites them. This is the last 

 act of the mind, in this centripetal direction in its prog- 

 ress from the multiplicity of facts to the central cause on 

 which they depend. But, having guessed the cause, we 

 are not yet contented. We set out from the center 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 experi- 

 ment: the suction-pump is but an imitation of the first 

 act of every new-born infant. Nor do I think it calcu- 

 lated 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 extracting 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 



