Feb. 23, 1888] 



NATURE 



38) 



I have made some inquiry, and am told that it is now commonly 

 employed by biologists, and especially by botanists, with that 

 meaning. 



As it would be very unfortunate if the same word were 

 habitually used in different senses by students of different 

 branches of science, may I be allowed to point out that, 

 according to the definitions of the C.G.S. system, a micromilli- 

 metre is the millionth of a millimetre. 



In the well-known Report of the Committee of the British 

 Association for the " Selection and Nomenclature of Dynamical 

 and Electrical Units " it is laid down that the prefixes mega and 

 micro are to be employed " for multiplication and division by a 

 million." 



This ruling has been generally accepted not only by scientific 

 men, but also by those engaged in commerce. Megohm and 

 microfarad are terms which are used in contracts, and are uni- 

 versally understooi to mean a million ohms and a millionth of a 

 farad respectively. It will be hopeless to try to introduce scien- 

 tific systems of measurement into the affairs of daily life if 

 scientific men themselves disregard the rules on which those 

 systems are framed. 



It would also be particularly confusing if the micromillimetre 

 were wrongly used by microscopists. In its proper sense it is 

 the most convenient unit in which to express molecular magni- 

 tudes. It has been employed for that purpose by Sir William 

 Thomson and others in England, and also by physicists abroad. 

 If the micromillimetre of the microscopist is 1000 times too 

 large, all sorts of mistakes will be rife as to the relative dimensions 

 of molecules and of the smallest objects visible with the micro- 

 scope. 



The proper name for the thousandth of a millimetre (/i) is the 

 micrometre, and though the similarity of this word to micrometer 

 is no doubt a drawback, it is not likely that confusion could often 

 arise between them. 



If, therefore, I am rightly informed as to the custom of 

 botanists in this matter, I beg respectfully to suggest that they 

 should bring their nomenclature of units of length into con- 

 formity with the definitions of the C.G.S. system. Otherwise 

 there will be a permanent confusion between the micrometre {/j.) 

 and the micromillimetre (/xfj.). Arthur VV. Rucker. 



Science Schools, South Kensington, February 17. 



"The Teaching of Elementary Chemistry." 



Allow me to draw the attention of the chemical section of your 

 readers to a few highly misleading passages in the two books 

 reviewed under the above heading in Nature of January 19 

 (p. 265). 



On p. 65 of the " Elementary Chemistry " we read: — 



" Hence when sodium and water interact, a portion of the 

 hydrogen which was combined with oxygen is evolved as hydro- 

 gen ga-j, and another portion enters into combination with the 

 sodium and the oxygen to produce caustic soda." 



On pp. 1 16-17 is to be found the following astounding 

 passage : — 



"To prepare Cl.^O, mercuric oxide (HgO) is heated in a 

 stream of dry chlorine. When mercuric oxide is heated it is 

 decomposed into mercury and oxygen ; therefore by passing 

 chlorine over heated mercuric oxide we carry out a reaction in 

 which oxygen is produced in presence of chlorine." 



In the "Practical Chemistry," under Experiment i, Chap- 

 ter II. (p. 6), occurs the following warning to the student : — 



" Do not remove the lid at any time for more than a second 

 or so, else some of the magnesia will be volatilized and lost ;" 

 while on p. 285 of the " Elementary Chemistry " we read : — 



" No compound of Mg has been gasified." 



Even this contradiction is excelled by one on pp. 62 and 63 

 of the " Practical Chemistry," which is not so manifestly a slip. 

 We read (p. 62) : — 



" The reactions between aqueous solutions of alkalies and the 

 three elements, chlorine, bromine, and iodine, are similar ; com- 

 pounds of similar compositions and similar properties are pro- 

 duced under similar conditions." 



Under Experiments 19 and 20, which follow, the student is told 

 to treat cold solutions of potassium hydroxide with chlorine and 

 bromine respectively. The well-known changes are described, 

 and the bleaching properties of the solutions after addition of a 

 little acid, are to be tried. Then follows (p. 63) : — 



"Exp. 21. Perform an experiment similar to 19 and 20, 

 but use iodine in place of chlorine or bromine : the liquid 



which is produced does not bleach. No compound of iodine 

 analogous to KCIO and KBrO has been obtained." 



Tnilythis is "seeing things as they are" with a vengeance. 



Z. 



Natural Science and the Woolwich Examinations. 



May I be allowed, as one of the most experienced science 

 masters in the public schools, to say a word in reply to Mr. 

 Gurney's letter in Nature of this week (February 16, p. 365)? 



There seems to me a general fallacy running through that 

 letter arising from "the absence (on the writer's part) of clear 

 discrimination" between the nature and methods of mathe- 

 matical science (which, as J. S. Mill taught us long ago, are 

 mainly deductive) and experimental science (which proceeds by 

 inductive methods). It is on this ground mainly, coupled with 

 the extent to which it cultivates the faculty of observation, that 

 we claim for it a special educational value. 



After an educational experience at least as extensive as Mr. 

 Gurney's, I join issue with him most distinctly on this point. I 

 am afraid there lurks behind Mr. Gurney's depreciation of the 

 educational value of science the disappointment which other 

 mathematicians have experienced in finding that the man who 

 takes to experimental science as a mere excursion-ground for the 

 diversion of the mathematician is not infrequently brought to 

 confusion by Nature. Science is something more than measure- 

 ment. Mr. Gurney's notion that mathematics and a knowledge 

 of French and German are a sufficient groundwork for true 

 scientific knowledge is such a confession on his part of the small 

 value he attaches to experimental demonstration and to labora- 

 tory training (or to field-work in the case of geology) as is 

 sufficient to put him out of court as a witness on this question. 

 Nor do I think that he is competent to speak with any authority 

 on the work done in the public schools. If he fancies that the 

 best boys of the public schools go to Powis Square to finish their 

 education, he is labouring under a delusion. 



The whole argument of the letter is retrogressive ; nor is it 

 strengthened by the writer's condemnation ol a "smattering" 

 of science, which is no discovery. But I maintain that a boy 

 can, by the age of eighteen, get a sound groundwork in science 

 laid, though not by the cramming system ; and that to this the 

 term does not apply at all. Again, he condemns premature 

 specialization of a boy's studies in favour of science, while he 

 inconsistently advocates a much narrower specialization in favour 

 of mathematical studies. 



How far Mr. Gurney is from being convinced by his own 

 arguments is shown by the fact that in the concluding paragraph 

 of his letter he practically surrenders the point on which the 

 whole question turns. 



In conclusion I would commend to his careful consideration 

 the letter which appears in the Times to-day from the head 

 ma.ster of Clifton College, whose competence to form a judg- 

 ment on the educational aspect of this question I suppose no 

 one doubts. A. Irving, 



Wellington College, Berks, February 17, 



With your kind permission, and in consideration of the 

 importance of the matter, I crave leave for space for a few 

 remarks in addition to those contained in my reply to Mr. 

 Gurney. 



(1) Looking at the history of education in this country, we 

 can account for, though we deplore the existence of, a prevalent 

 notion, a sort of fashionable superstition, which regards scien- 

 tific studies as outside the range of what is called " culture " ; a 

 superstition for which some of those who have fspoken in the 

 name of science are not altogether unanswerable, but which 

 derives its chief strength from that profound ignorance of natural 

 science — its nature, its methods, and its object — upon which so 

 large a proportion of educated Englishmen seem rather to pride 

 themselves than otherwise. There can be but little doubt that 

 this has been turned to account as an influence in favour of the 

 contemplated scheme. 



(2) It is in no spirit of hostility to literary studies that one 

 writes in these terms ; on the contrary, it is as a lover of 

 literature of the better sort that one would gladly see the literary 

 spirit in this country, as in Germany, strengthened and braced 

 by the strong atmosphere of scientific criticism, and a little more 

 first-hand acquaintance with things as they are, which is the true 



