March 27, 1913J 



NATURE 



97 



ordinary needs, but at times he meets a problem for 

 which his tools are useless. He may then spend 

 thousands of pounds on the determination of some 

 point which the mathematician could have settled for 

 a rive-pound note. Instead of collaborating, the 

 practical man and the mathematician scorn one 

 another with an equal scorn, and indulge in pin- 

 pricks when they happen to meet. It seems to us 

 that it is for the mathematicians, who are seeking 

 admission into the practical man's sphere, to hold 

 out the olive branch, to go to him and say : — " Yes, 

 we have often given you reason for thinking us fools. 

 But we think we can really help you this time. Only 

 let' us try; if we fail, you are no worse off than 

 before." 



Education of Girls and Women. 



No. 18 contains three papers by Miss Gwatkin, 

 Miss Burstall, and Mrs. Sidgwick. Miss Gwatkin 

 gives an effective statement of the advantages to be 

 gained by a girl from the study of mathematics. We 

 fear, however, that these advantages can only be 

 attained by exceptional girls, and that for the average 

 girl it is an attempt to turn a good girl into an 

 inferior boy, to implant masculine virtues in place of 

 developing the feminine ones. We could wish that 

 Miss Gwatkin had supplemented her statement by an 

 estimate of the relative advantages to the girl of 

 mathematics and of possible alternative studies. 



In the same paper Miss Burstall shows, in a his- 

 torical sketch, the chance wind by which mathematics 

 was introduced as a necessary element in the secondary 

 education of girls, and then proceeds to inquire how 

 far it is appropriate there. She is in general agree- 

 ment with the present tendency to give an occupa- 

 tional turn to school studies, and points out how little 

 connection mathematics has with the life of the bulk 

 of women. 



Miss Burstall divides girls into three classes. At 

 one end of the scale is the small number with a real 

 taste for mathematics. For these the subject is an 

 admirable training, provided the danger of "narrow- 

 ness, hardness, ossification," is avoided by requiring 

 a concurrent training in English literature or some 

 other literary subject. 



At the other end of the scale come a number of 

 girls who cannot do mathematics at all, or only with 

 an enormous expenditure of energy. The teaching of 

 these she compares to the laboratory manufacture of 

 diamonds, the cost of production being quite out of 

 proportion to the value of the resulting article. 



Between these two extremes lie the bulk of the girls. 

 For them mathematical training has value, but the 

 same attainment must not be expected of them as of 

 boys. The importance of other subjects and the girl's 

 total energy-supply have to be considered. They 

 should study mathematics for two or three years and 

 get what value they can from the study, but the assess- 

 ment of results by examination should not be forced 

 on every girl. In school-leaving and college-admission 

 examinations the necessary guarantee of austere intel- 

 lectual effort can be secured by making Latin or an 

 appropriate treatment of Harmony alternative with 

 mathematics. 



In a short and eloquent paper on university mathe- 

 matics for women, Mrs. Sidgwick maintains that 

 "there is no need to consider the case of women 

 separately from that of men," and that while "in 

 planning a scheme of general education regard must 

 be had to the probable future work of the learners, 

 a subject which is studied not for its own sake, but 

 because it is useful for something 1 else, is almost 

 always degraded in the process, and loses much of its 

 educational value." David Bf.veridge Mair. 



NO. 2265, VOL. 91] 



THE RUSTING OF IRON. 1 



I N the October issue of the Chemical Society's 

 -*• Journal, Mr. Bertram Lambert describes a second 

 series of experiments on the rusting of iron. In these 

 experiments it is shown by spectroscopic examination 

 that carbon dioxide was actually present under the 

 conditions used previously. Elaborate care was there- 

 fore taken to remove this, by heating as much as 

 possible of the apparatus, whilst maintaining a high 

 vacuum, and (during some of the successive heatings) 

 cooling an attached tube in liquid air. The spectro- 

 scopic indications of carbon dioxide disappeared after 

 the first of eight successive heatings, but no change 

 was noticed in the readiness with which commercial 

 iron rusted in the apparatus when purified oxygen and 

 purified water were admitted. The author maintains, 

 therefore, that these substances are capable of bring- 

 ing about rusting in the absence of any trace of 

 carbonic or other acid. The contrast between these 

 results and those observed by Moody and by Friend is 

 attributed to "passivity" induced in the metal in the 

 one case by treatment with_chromic acid (as suggested 

 by Tilden), and in the other case by treatment with 

 caustic soda (as suggested recently by Dunstan and 

 Hill). This passivity must evidently be supposed to be 

 permanent during many months of contact with air 

 and water, but to be destroyed immediately by the 

 merest trace of carbonic acid or by contact with glass. 



An interesting account is given of the properties of 

 pure iron as prepared by the methods previously 

 described by the autrror, in which ferric nitrate is 

 obtained so perfectly free from manganese that it no 

 longer shows the violet colour which usually char- 

 acterises the salt, and is then decomposed in iridium 

 vessels, so as to avoid all risk of contamination with 

 platinum. The metal so prepared is permanently 

 resistant to rusting, even in contact with common air 

 and common water. It does not dissolve in cold 

 dilute sulphuric and nitric acids, but dissolves readily 

 when the acids are heated. Hydrochloric acid dis- 

 solves the metal even in the cold. A similar contrast 

 is noticed in the behaviour of the salts ; the metal does 

 not rust when exposed to air in presence of sodium, 

 potassium, or ammonium sulphate or nitrate, but 

 undergoes corrosion in a few hours when transferred 

 to a normal solution of one of the chlorides. Again, 

 pure iron will withstand the action of a saturated solu- 

 tion of copper sulphate or copper nitrate at the 

 ordinary temperature for an indefinite time, without 

 losing any of its lustre and without any perceptible 

 trace of copper being deposited ; but if a concentrated 

 solution of copper chloride is used, the iron becomes 

 coated with copper immediately it is put into the 

 solution, and, within a few minutes, the iron all dis- 

 appears, and only finely divided copper remains. The 

 behaviour of the pure metal is here very similar to 

 that of commercial aluminium. 



The resistance of the purified metal to corrosion 

 and to dissolution is probably due to the homogeneity 

 of its surface, since if this is destroyed by pressing 

 the metal with an agate pestle in an agate mortar 

 the metal begins to corrode in less than an hour, rust 

 being deposited on the unpressed parts of the metal 

 whilst the pressed parts remain bright. In the same 

 way copper is deposited on the iron if it is pressed in 

 an agate mortar before being put into a solution of 

 copper sulphate, or if it is pressed with a quartz rod 

 while under the copper sulphate solution. 



As a rule iron which will not rust will not deposit 

 copper from the sulphate, and conversely; but in one 



1 See Nature. 1911, vol. Ixxxvi., p. 25. 



