522 



NATURE 



[October i, 1903 



If you mean by ' in ' that the constituents can be got 

 out again by appropriate means, then they are 'in.' 

 But you mustn't suppose that the constituents are 

 locked up in the compound, somehow or other, with 

 all their properties." 



So far, it might be supposed that this system does 

 not differ from the " heuristic " system which has been 

 so much in evidence lately. But that is not so. There 

 is no attempt made to prove anything exhaustively, or 

 to let the pupil do so ; as a rule, the experiment is made 

 by the teacher, and the pupil is sometimes allowed to 

 repeat it. A little later, in considering the 

 classification of certain elements, the pupil remarks, 

 " But it appears to me not very scientific to take any- 

 thing on trust that I can't prove." To which the 

 teacher answers, " You will be able to prove this, when 

 you know more chemistry." 



Teleological " explanations " are conspicuous by 

 their absence. Yet when the pupil inquires, " Why 

 have most chemical stuffs such a nasty smell? " he is 

 told, " If they hadn't, we shouldn't notice them, and 

 we should have our skin hurt and get a cold in the 

 head." This is not quite consistent. 



That the cost of an article depends on the amount 

 of work put into it is illustrated in the case of 

 aluminium, the compounds of which, such as clay, 

 have almost no value, while the metal is costly. 

 The pupil inquires, " Can the work be got out of the 

 aluminium again?" "Yes," says the teacher, and 

 shows the pupil the reduction of iron oxide by means 

 of powdered aluminium. 



The pupil is constantly afraid that he will not be 

 able to retain in his head all that he is taught. But 

 he is comforted by being assured that he will have to 

 go over the subject again, and that he really knows 

 a good deal. These little remarks are very natural, 

 and the answers are most judicious. But we agree 

 with the pupil when he says " Chemistry is a fright- 

 fully big subject! " Indeed, he is told that no one 

 man knows all about oxygen, in reply to a remark, 

 flattering to the teacher, " But surely you know all 

 about this! " Much is in writing, however; and he 

 then asks, " Is everything in these books right? " 

 " Most of it," he is assured; and what is best about 

 scientific books is that no one intentionally tries to 

 deceive. 



The action of iron oxide in accelerating the evolu- 

 tion of oxygen from potassium chlorate is likened to 

 that of oil on a rusty machine, or of a whip on a horse. 

 And so catalytic phenomena are introduced. There 

 are many such digressions, and often the teacher lets 

 them go on to a certain point, and then harks back to 

 th^ actual subject of the lesson. 



The pupil is introduced to the idea of mass-action 

 after he has made the natural remark, " But iron is 

 stronger than hydrogen, and takes the oxygen from 

 it." " First iron was stronger than hydrogen, and 

 afterwards, hydrogen stronger than iron. That's 

 surely a contradiction." "The contradiction is owing 

 to your looking at the reason of chemical changes as 

 a mechanical power or force; such a force has never 

 been proved to exist or measured. " And when pressed, 

 NO. 1770, VOL. 68] 



the teacher fences thus, " A man can carry a good lot 

 of water; but a larger quantity of water can carry a 

 man." " So you mean, chemical change depends on 

 which stuff is present in largest quantity," "That's 

 about it; but we must go back to hydrogen." And 

 the digression closes. 



The laws of recurrence and of continuity are illus- 

 trated and formulated ; the existence of allotropic forms 

 of carbon is referred to the difference in their content 

 of energy, and the source of all terrestrial energy, 

 except that of the tides, is traced to the sun, due atten- 

 tion being paid to the reciprocal action of plants and 

 animals. 



One admirable feature of the work is that the pupil 

 is allowed to fall into all kinds of traps. For example, 

 he calculates the conversion of the Fahrenheit into 

 the centigrade scale in every conceivable wrong 

 manner before he finds the right use of the "32""; 

 and after he has seen experiments on the com- 

 pressibility of air and the observations have been 

 written down, he is made to find the law. The method 

 is SO' good that It Is worth quoting. " Suppose you 

 have ten apples : some in your pocket, some in your 

 hand. Call the number of apples In your pocket t, and 

 those in your hand h. Now you know you can calcu- 

 late t if 3^ou know h, and h if you know t. Why is 

 that? " " Because I know that together they make 

 10." " You see then t+/i = io; and you can calculate 

 t if you know h, and vice versa." "That's neat. 

 But I could have done that without a formula." 

 " Yes ; but only because the formula is so simple. 

 Now try If your pressures and volumes can be calcu- 

 lated as simply." "Let me see: — 75+100=175; 

 62.5 + 120- 182.5; 60+150 = 210. No; the sum is 

 always getting bigger." "The sum formula doesn't 

 fit, then. You might have seen that you can only add 

 like things, such as apples to apples : you can't add a 

 pressure to a volume." "What sort of formula can 

 it be, then? " " If p gets bigger, v gets smaller. 

 What kind of combination of p and v will give that 

 result?" "Probably a whole lot." "Quite true; 

 but not many simple combinations. Try the simplest 

 you can think of, besides the sum." " Perhaps the 

 product. If one factor gets smaller, the other must 

 get larger, so as to make the same product." And so 

 he gets It out. 



It must be allowed that this is excellent teaching. 

 The whole book is so lively and conversational, 

 and withal so amusing, that it well deserves reading 

 by those of an older generation. It Is probably likely 

 to be more useful to teachers than to pupils, for it will 

 serve them as a guide. As the publishers say In their 

 preface, the standpoint from which the book Is written 

 is the most modern one; some, perhaps, may consider 

 It too modern, and that some of the doctrines ex- 

 pounded are as yet not In general circulation, and 

 perhaps never will attain universal consent. That is 

 a matter of opinion, and, of course, the author believes 

 that they will. Anyhow, he has taken advantage of 

 the lessons of all missionaries^ — get hold of the 

 children, and the doctrines will spreads And If an 

 attractive book can help their dissemination, this is. 

 one. W. R. 



