January 24, 1901] 



NA TURE 



313 



are issued by the Survey for the more important Atlantic 

 harbours, as well as for the Pacific coast of Canada. The tides 

 are complicated by a great variation in range, and the observa- 

 tions secured will serve also as a basis for future investigation 

 of the currents, many of the strongest of them being tidal in 

 their nature. 



THE ABSORPTION SPECTRA OF SALINE 

 SOLUTIONS. 



IN the Scientific Transactions of the Royal Dublin Society 

 (vol. vii. series ii. pp. 253-312), Prof. W, N. Hartley 

 gives the results of a long series of experimental investigations 

 which he has undertaken to determine the action of heat on the 

 absorption spectra and chemical constitution of saline solutions. 

 After reviewing previous researches by Schoenbein, von Babo, 

 Schiff, Gladstone, Bunsen, Melde, Burger, Vogel, Landauer, 

 Morton, Bolton and Russell, the author gives a description of 

 his mode of experimenting. Wedge-shaped cells containing 

 the liquids under examination were heated in an air-bath with 

 glass sides. The sources of light used were sunlight and an 

 argand burner fed with oxygen. 



Then the absorption spectra of solutions of the salts of nickel, 

 copper, cobalt, chromium, uranium, didymium, and various per- 

 manganates are described, with details of the measurements, ac- 

 companied by drawings from, or reproductions of, the photo- 

 graphed spectra. Much of the discussion is directed to the 

 bearing of the spectral evidence as to the constitution of the 

 solutions, and the following conclusions indicate the results 

 arrived at : — 



(i) The absorption spectra of different salts of the same 

 metal, whether solid or in solution, are not identical, even 

 when the spectrum is a marked characteristic of the metal. 



(2) When a definite crystalline hydrate dissolves in a solvent 

 which is not water, and is not a dehydrating agent, the molecule 

 of the salt remains intact. 



(3) In any series of salts which are anhydrous, and which 

 do not form well-defined crystalline hydrates, the action of heat 

 up to the temperature of 100° C. does not cause any further 

 alteration in their absorption spectra beyond that which is usual 

 with substances which undergo no chemical change by such 

 rise of temperature. The change is usually an increase in the 

 intensity of the absorption, or a slight widening of the absorption 

 bands. 



(4) As a rule the crystallised metallic salts, in which water is 

 an integral part of the molecule, dissolve in water at ordinary 

 temperatures without dissociation of the molecule. 



(5) Crystallised hydrated salts, dissolved in a minimum of 

 water at 20° C. , undergo dissociation by rise of temperature. 

 The extent of the dissociation may proceed as far as complete 

 dehydration of the compound, so that more or less of the an- 

 hydrous salt may be formed in the solution. 



(6) The most stable compound which can exist in a saturated 

 solution at 16° or 20° C. is not always of the same composition 

 as the crystalline solid at the same temperature, since the solid 

 may undergo partial dissociation from its water of crystallisation 

 when the molecule enters into solution. 



(7) Saturated solutions of hygroscopic and deliquescent 

 salts combine with water when diluted to constitute molecules 

 of more complex hydrated compounds in solution. 



(8) When a saturated solution of a coloured salt undergoes a 

 great change of colour upon dilution, or any remarkable change 

 in its absorption spectrum due to the same cause, the. dilution is 

 always accompanied by considerable evolution of heat. 



CONFERENCE OF SCIENCE MASTERS IN 

 PUBLIC SCHOOLS. 

 IXTHILE carrying out the important work of spreading 

 scientific instruction in this country, our educationists 

 should make themselves quite sure that the teaching already 

 inaugurated is what it claims to "be. Care must be exercised 

 in order that a training in habits of exactness and observation 

 is imparted, as well as an appreciation of the principles of 

 science quite apart from a mere knowledge of facts. By intelli- 

 gent practical work upon the part of the individual scholar this 

 alone can be attained, and under present circumstances such 

 exercise is difficult to successfully organise in schools. 



Expensive laboratories and able masters are of no avail if the 



NO. 1630, VOL. 63] 



necessary conditions be not introduced. The scientific staffs of 

 our large public schools are fully aware of their responsibility 

 to the nation, and what is lacking to enable them to fulfil it. 

 It might, therefore, be thought that they would have been 

 the very first to advocate the necessary changes, but their 

 position, it will be seen, is such a peculiar one that, without 

 strong general feeling behind them, their trouble would be all 

 thrown away. 



With the dawn of the new century, however, and in view of 

 the present agitation for an improved system of scientific educa- 

 tion, the public school science masters have combined all their 

 energies for the attainment of that end. On January 19, there- 

 fore, a conference was held at the rooms of the University of 

 London, and was attended by a thoroughly representative body 

 of men. Sir Henry Roscoe, Vice-Chancellor of the University, 

 and a member of the governing body of Eton College, occupied 

 the chair, and explained the importance of the action taken. 



Among the papers read, that by Mr. Oswald H. Latter, 

 of Charterhouse, contained perhaps the most general observa- 

 tions. " Science teaching," he told us, "was first introduced 

 into our public schools as a sop to a growing public opinion, and 

 with a desire to impart a gentlemanly acquaintance with scientific 

 matters. The broad-minded persons who ventured on this new 

 departure imagined, unfortunately, that the admirable mediaeval 

 methods of classical and mathematical teaching were equally 

 well suited to the new comer, who, however, had to be content 

 with a very small portion of the temporal possessions of its 

 'elder bretheren." Mr. Latter then urged the neces.«ity of a 

 scientific education for future legislators, and our commercial 

 and professional men, and from a national point of view. Form 

 teaching would do much, he considered, to remove the incubus 

 of ignorance and apathy in the coming generation, the following 

 tieing his recommendations with regard to it: — 



(i) Science should be raised to the dignity of a "form 

 subject," and no longer be regarded as a more or less negligeable 

 extra. It should enter for at least one hour into the ordinary 

 work of every day, and claim, at any rate, some portion of the 

 time devoted to preparation. There must be some lopping of 

 the old branches of education if good fruit is to be borne by the 

 engrafted scion. 



(2) A classification according to proficiency in science through- 

 out the school. 



(3) At least half, and with lower forms more than half, of the 

 allotted hours should be devoted to systematic laboratory work 

 in the elements of physics and chemistry. 



(4) The teaching should be continued to the sixth forms 

 instead of being deliberately withheld from them as is so often 

 the case, a distinction which at once narrows the intellectual 

 horizon of the ablest boys in the school, and degrades the 

 subject in the eyes of the remainder. 



Mr. E. E. Ashford, of Harrow, would with very good reason 

 teach some physics before chemistry, and, if possible, element- 

 ary biology before eidier, for, he said, let us first use the facts a 

 boy knows to teach the methods of science. All boys, he con- 

 tinued, are acquainted with many bits of natural history, and its 

 general laws were more easily appreciated than the more exact 

 ones of the other sciences. The paper by Mr. Ashford con- 

 cluded with the following resolution, which found favour with 

 the meeting, viz., that "it is essential that every boy before 

 leaving school should go through a course of practical measure- 

 ment and experiment involving no previous theoretical know- 

 ledge." 



Prof. Armstrong, who was present, true to his tenets that 

 academic words should not be used in schools, suggested 

 nature-study in place of biology, but the terms were not recog- 

 nised as synonymous by several speakers, and so he was some- 

 what misunderstood. Mr. A. Vassall, in describing the work 

 at Harrow, recommended that the biological lessons should 

 form a continuous course, and it must be remembered that the 

 boys (over fourteen and under sixteen years of age) he teaches 

 are not tiny children for whom unconnected object-lessons are 

 best adapted. The list of lessons given to the conference well 

 illustrated Mr. Vassall's plea for the "judicious skipping" of 

 subjects not quite suitable for introductory work. Mr. Gumming, 

 of Rugby, used, he said, to teach all his boys botany ; he owned, 

 however, that he had no qualifications but a love of the subject, 

 and it is not surprising that the other sciences he has since 

 substituted have succeeded better. 



Mr. W. D. Eggar, of Eton, pointed out that, owing to ex- 

 ternal pressure, many public schools had started elementary 



