February 26, 1903 J 



NA TURE 



39i 



without whom nothing can be done, the men whom we all 

 admire so much that we almost forget their faults— I ask 

 them to translate our poor ideas, our platitudes, our truisms, 

 our copy-book maxims as to what ought to be done, into 

 actual performance. The wonderful papers or books that 

 they are now writing, can these make their names glorious 

 for 'more than fifty or a hundred or a few hundreds of years? 

 Is this fame to be weighed against the greater reward we 

 offer? They have the chance of causing mathematics to be 

 made a mental tool always ready for use by the engineer 

 and physicist, the pioneers of thought and civilisation in 

 this stage of the world's history. We ask them to take a 

 high view of the value of their opportunities ; really to lead 

 the vanguard in the attack now at last being organised 

 against the general -ignorance of our people. 



Let them think of all the university colleges and engineer- 

 ing schools of the country, and consider how disgust at 

 useless routine has led to general neglect of duty in teacher 

 and taught. I know of a college where two senior wranglers 

 in succession have taken charge of the education of the 

 average student, and there has been no teaching of mathe- 

 matics for many years. I know of another college where 

 another senior wrangler does his best to maintain the old 

 tradition that a man paid to teach ought to know nothing 

 nl ti nhing, ought to care nothing for teaching, and ought 

 to feel insulted if the persons who pay him his salary happen 

 to mention efficiency of teaching in his presence. I acknow- 

 ledge that these professors are of the salt of the earth ; they 

 have done great service to science by their own work ; they 

 ought to be encouraged to do more and more of the work 

 that they are specially fitted to perform, but 1 do say that 

 it is a shame to sacrifice all their students because it happens 

 that Cambridge has not enough endowment for such men. 

 Fifty years ago it did not matter to us if 90 per cent, of the 

 undergraduates at Cambridge made fun of mathematics. It 

 matters to us now very much indeed that the most important 

 weapon that any modern nation can have, the power to com- 

 pute, should be jeered at by the very men, the engineers, who 

 could make most use of it if they only knew how. This is 

 my excuse for what seems a great presumption in criticising 

 Cambridge and in asking that my ideas shall have a careful 

 consideration. I want to see schemes drawn up for the 

 education of all kinds of civil and military engineers. The 

 courses of study fnust be made interesting and useful. I 

 do not wish to find that a sailor who has worked out all 

 Napier's and Gauss's analogies has never measured a dis- 

 tance with a tape line on a terrestrial globe, or that he 

 cannot do " the day's work," as it is called, without using 

 seven or six figure logarithms. 



It is surely an awful thing that many earnest men, because 

 they have faith in us, should be induced to spend years in 

 making ropes of sand. At the end of long academic courses 

 an examiner finds the best students to be quite satisfied 

 with sand-rope making, and mathematics will be as much 

 detached from their professional work as the game of 

 patience is detached from the daily avocation of the lady 

 who plays it. As for the average men who hate the whole 

 thing, they are better off ; I mean, of course, if they manage 

 to pass their examinations, for they can look before and 

 alter, and need not pine for what they never had. 



The nation feels that its common sense has been outraged, 

 and it is not merely elementary education that is going into 

 the melting-pot. Is Cambridge going to hold aloof from 

 the little army of men who think that the melting and 

 solidifying processes need to be guided? Has Cambridge 

 no interest whatsoever in the nature of the possible crystal- 

 lisation? 



There is no great engineering school the mathematics of 

 which ought not to be in charge of as fine a mathematician 

 as a salarv of 1500?. or 200oi. a year can tempt ; is this man 

 to be a Cambridge man? 



Let Cambridge make no mistake as to the issue now 

 before us. We know she can do what we want if she likes 

 to set herself to it, and we are willing to coax her, for we 

 owe her much. We shall take care that her very highest 

 ideals are not interfered with ; if she makes mathematics 

 popular, pleasant and useful to practical people, she will 

 receive back again such great pupils in pure and applied 

 mathematics as she does not dream of now. 



John Perry. 



Radio-activity of Ordinary Materials. 



In connection with Mr. Strutt's article on this subject in 

 this week's Nature, I may mention that I have received for 

 publication from Prof. McClennam and Mr. Burton, of the 

 University of Toronto, the manuscript of a paper read before 

 the American Physical Society in December last, on the 

 saturation current in cylinders of the same size but of 

 different materials. The cylinders used were 25 cm. in 

 diameter, and were made of zinc, tin and lead ; the current 

 in the lea'd cylinder was about twin- that in the zinc, and 

 about 50 per cent, greater than in the tin. The authors 

 found that the current in the cylinders was considerably re- 

 duced by immersing the cylinders in a large cistern full of 

 water, indicating that part of the ionisation is due to very 

 penetrating radiation which gets through the sides of the 

 cylinder. I may take this opportunity of stating that I 

 have found that lead apparently gives off an emanation 

 similar to that emitted by radium, for if lead acetate or lead 

 nitrate be dissolved in distilled water, and air very slowly 

 bubbled through the solution, the air coming out has greater 

 conductivity than if it had been bubbled through the dis- 

 tilled water alone, and it retains this additional conductivity 

 for many hours. We hope to investigate the effect of other 

 metals in solutions and to determine whether or not it is 

 due to the radio-active impurities in the salts. 



J. J. Thomson. 



Cavendish Laboratory, Cambridge, February 21. 



Fall of Coloured Dust on February 22-23. 



I have received this morning from two of the observers 

 of the Royal Meteorological Society samples of red or muddy 

 rain which fell on Sunday night or Monday morning. 



Mr. C. Grover, of the Rousdon Observatory, Devon, on 

 Monday morning, February 23, found that the windward 

 sides of the thermometer screens were conspicuously marked 

 with a deposit of reddish or rusty coloured mud, so thick 

 as to attract attention at once. There was the same appear- 

 ance on the anemometer tower — the window ledges, the iron 

 ladder and the white painted wooden shelf thirty feet above 

 the ground being all marked with the same deposit. The 

 rainfall was only o'02 inch. 



Mr. J. W. Phillips, of Haverfordwest, says that rain fell 

 between 6 and 9 a.m. on Monday, and that when the rain 

 gauge was examined the water was found to have a sedi- 

 ment of dust. The quantity of rain measured was o'3i 

 inch. Mr. Phillips says that the phenomenon has been 

 noticed in other parts of the country. 



The deposit at Rousdon was apparently much thicker 

 than at Haverfordwest. The fall must have extended over 

 a wide area. W.m. Marriott. 



Royal Meteorological Society, S.W., February 24. 



Chapman's Zebra. 



In the course of some studies of the genus Equus, I obtained 

 a number of measurements of the skulls of zebras and quaggas 

 through the kindness of Mr. J. A. G. Rehn. The measure- 

 ments were based on specimens contained in the collection of 

 the Philadel phia Academy of Natural Sciences. Upon comparing 

 these data, I found that the measurements for Equus chapmani did 

 not approach most nearly those of E. burchelli, of which chapmani 

 is supposed to be a variety. Roughly speaking, if the resem- 

 blance to burchelli were expressed by 4, that to E. zebra would 

 be expressed by 6, that to E. grevyi by 3, and that to 

 E. quagga by I. 1 In particular, E. zebra and chapmani had 

 the zygomatic breadth and the breadth between the orbits above 

 much less than in burchelli. The specimen of chapmani was 

 said to be from Zanzibar. Part of the facts observed may be 

 due to immaturiiy, and Mr. Oldfield Thomas warns me 

 that the precise identification of E. chapmani is a matter of 

 doubt ; but from what I have been able to learn, it seems not 

 impossible that- E. chapmani, as represented by Prof. Ewart's 

 " Matopo," may be a valid species. As it is quite out of the 

 question for me to settle this matter, I venture to commend it 

 to such of your readers as have better opportunities. 



T. D. A. COCKERELL. 



East Las Vegas, N.M., U.S.A., January 23. 



1 These figures are based, not on the absolute measurements, but on the 

 measurements expressed in percentages of the total length of the skull. 



NO. 1739, VOL. 67] 



