May 22, 1891.] 



SCIENCE. 



285 



bent round at the opposite end, so as to form a foot; the 

 wire is set upright in a dish full of water, and a large 

 pickle-jar is inverted over it, with its mouth in the water. 

 The iron is thus shut up over water along with air. Gradu- 

 ally the iron rusts, and concurrently the water rises in the 

 jar, showing that the air is concerned, as no rise is observed 

 in a comparison experiment without the iron. But after a 

 time the water ceases to rise: measurement shows that only 

 about one-fifth of the air disappears. Clearly, therefore, 

 the air is concerned. The experiment is repeated, and the 

 same result obtained; fresh iron is put into the residual air, 

 and still no change results: hence it follows, that, although 

 the air plays a part in the rusting of iron, the air as a whole 

 is not active, but only one-fifth part of it, which serves to 

 suggest that the air is not uniform, but has parts. Consider 

 the importance of the lesson thus learned, the number of 

 discoveries made by a few simple quantitative experiments, 

 the insight into exact method which is gained by a thought- 

 ful worker. 



To pass to my second example, — the discovery of the 

 composition of chalk. How is this to be effected? I would 

 call attention to what is known about chalk by people gen- 

 erally, — what it is like, where it occurs, and what it is used 

 for, — and ask whether there is no well-known fact con- 

 nected with chalk which will serve as a clew, and enable us 

 to apply our detectives' method. One of the great uses of 

 chalk is for making lime, which is got by burning chalk. Is 

 there any thing known about lime which shows that it di£fers 

 from chalk? Yes, when wetted, it slakes and much heat is given 

 out, while chalk is not altered by wetting; when the experi- 

 ment is made quantitatively, lime is found to increase about 

 33 per cent in weight on slaking. Let us then study the 

 conversion of chalk into lime by burning, and, as our un- 

 aided eyes tell us nothing, let us call in the aid of a balance. 

 A weighed quantity of chalk is strongly heated, and is found 

 to grow lighter; after a time, no further loss is observed, 

 and, when this is the case, the loss amounts to, say, about 

 43 per cent ; on repeating the experiment, the same result is 

 always obtained, and therefore it cannot be an accident that 

 the loss amounts to only about 43 out of every 100 parts of 

 chalk. What conclusion are we to draw? Evidently that 

 the stuff composing chalk consists of lime-stuff plus some- 

 thing else which is driven off when the chalk is burned. 

 What is this something? Can't we catch it as it is given off? 

 (We can, but the experiment is difficult, requiring special 

 appliances, owing to the high temperature required to burn 

 chalk in a close vessel). If not, is there no other clew which 

 can be followed? Yes, there is. It is to be supposed that 

 at an earlier stage in the experiments, attention will have 

 been directed to the way in which discoveries were made in 

 early times ; to the fact that various substances were found 

 to act upon each other, giving new substances; and that 

 when a new substance was discovered its action on the pre- 

 viously known substances was studied; that in this way va- 

 rious acids were discovered ; and that it was found out that 

 these were powerful solvents of metals, earthy substances, 

 etc., of chalk, among other substances. What happens to 

 chalk when thus dissolved in an acid? The experiment is 

 tried, and it is found that an air-like substance or gas escapes 

 as the chalk dissolves. How does lime behave with acid? 

 It is found on trial to dissolve, but no gas is given off. May 

 it not be, then, that the gas which is given off when chalk 

 becomes lime is also given off when chalk is acted on by 

 acid? Let us find out how much gas is given off in this 

 latter case. A weighed quantity of chalk is dissolved in 



acid and the gas measured, a simple apparatus being used, 

 like that figured in the last "British Association Report" 

 (Nature, April 33, 1891). It is found, when several ex- 

 periments are made, that, on the average, about 22,000 cubic 

 centimetres of gas are given off per 100 grams of chalk; and 

 chalk is thus shown to be characterized not only by the per- 

 centage of lime which it yields, but also by the amount of 

 gas which it affords when dissolved in acid. 



What is the weight of the gas that escapes ? The experi- 

 ment is carried out (by means of a very simple apparatus), 

 and the all-important discovery is made that the weight of 

 the escaping gas is just about what was lost on burning 

 chalk. There caa be little doubt, therefore, that the gas 

 thus studied is "the something" which is given off when 

 chalk is burned. If so, perhaps it may be possible to re- 

 associate this gas with lime, aud produce chalk. Lime is 

 therefore exposed in an atmosphere of the gas, and the in- 

 crease in weight determined; it is eventually ascertained 

 that the lime increases in weight to the extent required on 

 the assumption that it is reconverted into chalk; and on ex- 

 amining the product it is found to behave as chalk both 

 when heated and when dissolved in acid. Thus the problem 

 is solved, and it is determined that chalk-stuff consists of 

 lime-stuff and chalk-gas. I employ these terms advisedly, 

 and advocate their use until a much later stage is reached, 

 when systematic nomenclature can be advantageously made 

 use of. 



In talking about chalk, it may be pointed out that chalk 

 is believed to consist of skeletal remains and shells of sea- 

 animals; and, when the composition of chalk has been as- 

 certained, the suggestion comes naturally to examine shells. 

 When their behavior on burning and towards acid is studied 

 quantitatively, results are obtained which place it beyond 

 doubt that they essentially consist of chalk-stuff. The chalk 

 studies thus become of very great importance, and may be 

 made to cover a wide field. 



It is not to be denied that there are difficulties connected 

 with such teaching as that I am advocating, but it is a libel 

 on the scholastic profession to assert that the difficulties are 

 insuperable. I am sure that in this case the old ever-true 

 saying may be quoted, " Where there's a will there's a way." 

 Such teaching has not yet been given simply because there 

 must be less class-teaching, more individual attention, an 

 adequate proportion of the school time must be devoted to 

 the work, and properly trained, sympathetic teachers must 

 be called in to give such instruction. 



When scientific method is taught in schools, there will in- 

 evitably be a great improvement in school-teaching gener- 

 ally ; it will be carried on in a more scientific manner, and 

 new methods will be introduced. Indeed, I have already 

 learned from a head master in whose school experimental 

 science-teaching is receiving much attention, that the leaven- 

 ing effect on the teachers of some other subjects in the school 

 is quite remarkable, aud that they are clearly being led to 

 devise more practical modes of teac 



Photography and the lantern, also, are modern weapons 

 of great power, which often enable us to clothe the dry bones 

 of otherwise unattractive subjects with pleasing drapery. 

 And here the parent can often intervene with great effect. 



[Prof. Armstrong, in conclusion, drew attention to several 

 " logs " kept by young children, illustrated with photographs, 

 and insisted on the educational value of such work, owing 

 to the opportunity which it afforded of directing attention to 

 various matters of interest, and of impressing useful infor- 

 mation on the memory.] 



