[02 



NA TURE 



[November 30, 1899 



results unless plenty of ash constituents are present, phos- 

 phates as well as potash ; paragraph 20, that phosphates 

 are a highly desirable addition in the manuring of barley ; 

 and paragraphs 24 and 27, that both phosphates and 

 potash should be used on potatoes and on grass-land 

 when sulphate of ammonia is used to supply nitrogen. 



The Committee is to be congratulated on having 

 secured and published a very useful and very justly 

 written essay. 



Euclid. Books I. -IV. Edited by Charles Smith and 

 Sophie Bryant. Pp. viii + 288. (London : Macmillan 

 and Co., 1899.) 

 With this book we have another addition to the great 

 number of text-books on the Elements of Geometry. 

 Its chief features seem to be that the editors endeavour 

 to instil into the students the notion that it is the cor- 

 rect reasoning and proof of the propositions which should 

 be mastered, and not so much an exact repetition of the 

 words of the text-book or teacher. 



Abbreviations are freely used early in the first book, 

 and these should be adopted generally by beginners, as 

 the reasoning of a proof can be more easily scanned. 

 The editors have in several cases departed from Euclid's 

 solutions and adopted in their stead more modern and 

 simple methods. Included in the text are many examples, 

 both original and selected, from mathematical journals 

 and examination papers. In this form the Elements 

 should be found useful in many schools. 



Sylvia in Flowerland. By Linda Gardiner. Pp. 198. 



(London : Seeley and Co., Ltd., 1899.) 

 An attempt is here made to employ the methods of Lewis 

 Carroll in the teaching of botany. In the first chapter 

 the foxglove explains : " This is Leap Year with us (the 

 flowers), and so we have a thirty-first of June," and 

 because the thirty-first of June does not occur every year, 

 it is a day of special favour to humans, who are allowed 

 " to hear with both eyes and ears." Sylvia talks with 

 plant after plant, and is instructed by them in the 

 fascinating mysteries of cross-pollenation and many other 

 interesting questions of plant-life. The jam is some- 

 times scarcely thick enough to hide the powder ; but we 

 have little doubt that the volume will find many appre- 

 ciative readers. 



Magnetism and Electricity. By J. Paley Yorke. Pp. 



viii + 264. (London : Edward Arnold, 1899.) 

 Mr. Yorke's object is to provide an introduction to this 

 branch of physics for those students who already possess 

 some acquaintance with general elementary science. His 

 treatment is non-mathematical, and no precise in- 

 structions are given for experimental work. It is a little 

 difficult to understand the reason for the interpolation of 

 chapter v., headed "Electricity," between the subjects of 

 magnetism and the study of electric currents, more 

 especially as the subject of electrostatics is resumed in 

 chapter xii. The explanations are clear and simple, and 

 the book should give an intelligent reader sound pre- 

 liminary conceptions of an important subject. 



Field and Folklore. By Harry Lowerison. With a 

 chapter on Folklore by Alfred Nutt. Pp. vii -h ^-j. 

 (London : David Nutt, 1899.) 

 The collection of short essays on various aspects of 

 nature-study collected here should do a great deal to- 

 wards enlisting the sympathy of school teachers in de- 

 veloping a love in their pupils for outdoor observations of 

 animal and plant-life. Mr. Lowerison gives, in an in- 

 formal way, a series of useful hints as to how to set about 

 observing nature, and what books to consult to find the 

 explanation of observations which are not at first easily 

 understood. Mr. Nutt's chapter describes the scope of 

 folklore and the aims of students of this department of 

 knowledge. 



NO. 1570, VOL. 61] 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. '\ 



The Stockholm Conference on the Exploration of the 

 Sea. 



I CANNOT refrain from addressing to you a few words in. 

 support of Prof. Ilerdman s remarks on the outcome of the 

 Stockholm Conference. With marine biology so eminently re- 

 presented at the meetings, there was ground for an expectation 

 that the report would contain primarily recommendations for 

 work at sea. The representatives of chemical and physical 

 work appear to have known their minds and to have obtained 

 the just recognition of their claims. 



Hitherto in biological investigation work has been too ex- 

 clusively devoted to the food fishes themselves — too little to the 

 food of these fishes — far too little to their biological environ- 

 ment. It will be to many eager students, both of fishery affairs 

 and marine biology, a matter of dismay if nothing more definite 

 results from this Conference. There are, and have been, too- 

 many committees, secretaries and bureaus engaged on this sub- 

 ject. As Prof. Herdman says, we want work at sea. To be 

 precise, we want, to begin with, two well-equipped trawlers- 

 and the right men in them. If the Stockholm Conference had 

 recommended even one, it would have been a sign of grace. 

 Such boats are not mere scientific instruments — not merely the 

 luxuries afforded by governments in times of prosperity — but 

 sound financial investments in fishery affairs. The Norwegian 

 Government has, I understand, ordered one, admirably devised 

 for marine investigation. George Mitrrav. 



November 25. 



Bust of Sir George Stokes. 



You were kind enough to say last June that Mr. Hamo- 

 Thornycroft would undertake the production of bronze copies 

 of the presentation bust of Sir George Stokes, about one-third 

 of the size of the original, at a cost of seven guineas each, in 

 case twenty-five were ordered, and that names would be 

 received by Sir William Crookes and myself. 



If anybody wants such a copy I hope that he will write to 

 me at once. John Perry. 



Royal College of Science, London, South Kensington, S.W., 

 November 22. 



A Geometric Determination of the Median Value of a 

 System of Normal Variants, from two of its Gentiles. 



A SHORT account appeared in Nature, October 12, p. 584, 

 of a paper read by me at the British Association, entitled the 

 " Median Estimate," which will appear in the forthcoming 

 Journal of the Association. Its object was to solve a problem of 

 the following kind : — 40 per cent, of the members at a meeting 

 vote that a proposed grant should be less than 100/. , 80 per cent, 

 vote that it should exceed 500/. What is the Median Estimate, 

 supposing the normal law of frequency to hold good ? That is 

 to say, What is the sum that one-half of the members would 

 think too little, and the other half too much, and which there- 

 fore presents the best compromise between many discordant 

 opinions? I showed that the calculation was exceedingly 

 simple if certain tabular values are used that will be spoken of 

 later. But, on after reflection, it seems to me that further sim- 

 plification is both desirable and feasible. The problem is 

 representative of a large class of much importance to anthro- 

 pologists in the field, few of whom appear to be quick at arith- 

 metic or acquainted even with the elements of algebra. They 

 often desire to ascertain the physical characteristics of races 

 who are too timorous or suspicious to be measured 

 individually, but who could easily be dealt with by 

 my method. Suppose it to be a question of strength, as 

 measured by lifting power, and that it has been ascertained that 

 a per cent, of them fail to lift a certain bag a of known weight, and 

 that b per cent, of them fail to lift another heavier bag B. From- 

 these two data, the median strength can be determined by the 

 simple method spoken of above, and not only it but also the 

 distribution of strengths among the people. Having indicated 



