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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



on the structure of corresponding parts and the 

 development of the colt, involve reasoning of a 

 rather more abstract kind. But the whole of this 

 evidence may be fairly presented to a mind which 

 is still incompetent to form that general concep- 

 tion of the uniformity of Nature which makes 

 the directly inorganic origin of man a supposition 

 not to be seriously entertained for a moment. To 

 grasp the idea of any law of Nature requires a 

 considerable effort of abstraction, and that the 

 idea may be of any real use it must be founded 

 on acquaintance with the facts that come under 

 the law. The general conception of law which is 

 contravened by the supposition in question has to 

 be abstracted from a knowledge of many differ- 

 ent laws, dynamical, physical, chemical, biologi- 

 cal. This conception, therefore, implies a very 

 wide and many-sided training in facts, a very deep 

 and thorough training in logic, as its foundation. 

 Much education is required to enable the learner 

 really to estimate the evidence for the many-toed 

 horse ; much more is wanted for the clear compre- 

 hension of the evidence for the simpler-brained 

 man. 



Here the education question, which has been 

 underlying our whole discussion, is brought to 

 the front. It is clear that the evidence for these 

 doctrines cannot be taught until a late period in 

 education. What are we to do in the earlier pe- 

 riods? Shall we say: "Horses had three-toed 

 and four-toed ancestors ; by-and-by you will 

 learn how this was found out. We think, but 

 are not quite sure, that men had simple-brained 

 ancestors ; by and-by you will learn why we think 

 so?" 



It seems to me that this is the very worst 

 thing we can do ; that, if we say this, we shall 

 not only confuse the child's head at the time 

 with abstractions which it is impossible that he 

 should really grasp, but we shall effectually pre- 

 vent him from learning them properly in the fu- 

 ture. The true rule, I believe, is this: Before 

 teaching any doctrine, wait until the nature of the 

 evidence for it can be understood. 



This appears at first sight a very hard thing 

 to do. Yet it is really involved in Pestalozzi's 

 great principle that children should be made to 

 find out things for themselves. To make clearer 

 the reasons for it, I will consider a case which 

 has the advantage of not being at the present 

 moment in controversy ; the case of the teaching 

 of chemistry. Suppose we were to begin teaching 

 chemistry by saying that carbon is made up of 

 atoms which have four hooks or hands by which 

 they can hold on to other atoms ; that oxygen- 



atoms have two hooks, and hydrogen-atoms one. 

 Consequently, we can hook two hydrogen-atoms 

 to an oxygen-atom, and this makes water; or we 

 can hook two oxygen-atoms to a carbon-atom, 

 making carbonic acid ; or we can hook four hy- 

 drogen-atoms to a carbon-atom, making marsh- 

 gas. Then we should utterly confuse the learn- 

 er's mind, and prevent him from learning chem- 

 istry afterward. These statements belong to the 

 doctrine of atomicities. Nobody doubts that 

 these statements represent, in highly-metaphori- 

 cal language, real facts of chemical action ; only 

 Sir Benjamin Brodie says that, since the hydrogen- 

 atoms occur always in even numbers in com- 

 pounds made of carbon, oxygen, and hydrogen, 

 we ought to fasten them together in pairs, and 

 call each pair an atom with two hooks. What 

 sort of thing we should find, if we knew all about 

 these atoms, answering to the metaphor of the 

 hooks, nobody knows. Without a knowledge of 

 the facts which they symbolize, these statements 

 are mere useless nonsense in anybody's mind. 

 They are worse than useless ; for they make him 

 think he knows the facts, and so prevent him 

 from really getting to know them. 



On the other hand, we may follow Dr. William- 

 son's method, show the children how to make 

 carbonic acid, and then pour it on a candle to 

 put it out ; burn hydrogen to produce water, and 

 so forth. When a few of the commoner sub- 

 stances are real things to them, whose properties 

 they are familiar with, they may learn to weigh 

 and measure. Then the law of definite propor- 

 tions becomes legitimate teaching, and the law of 

 gaseous volumes. It is only necessary to verify 

 these in a few cases, that the nature of the evi- 

 dence for them may be understood. 



Here arises a typical question. How, at this 

 point, shall we deal with the doctrine of mole- 

 cules ? The chemical evidence for it may now 

 be clearly understood ; but the chemical evidence 

 leaves it still an hypothesis. It becomes quite 

 clear that the hypothesis explains the facts, and 

 links them together; but it docs not become 

 clear that no other hypothesis will explain the 

 facts. I think there is every reason why it 

 should be 'taught as an hypothesis ; there are 

 materials in the pupil's mind for estimating the 

 value of the hypothesis in making the facts clear 

 to him, and also for understanding why, at pres- 

 ent, it is only hypothesis. And I further think 

 that, at this stage, no great harm will be done by 

 telling him that, when he has learned enough 

 about heat and motion, he will find the hypothesis 

 turned into a demonstrated fact. 



