August 24, 19 16] 



NATURE 



:)3d 



sional rotation. We are justified in assuming that this 

 free precessional period is constant in duration and 

 therefore determines the average rate of rotation of 

 the pole of revolution. If, therefore, we take a 

 diagram of the polar movement, which will naturally 

 have its axes of reference fixed in relation to the earth, 

 and convert it into another diagram, showing the 

 same movement, referred to axes rotating in the earth 

 at the average rate of the precessional rotation, we 

 obtain a graph of the irregular part of the polar path. 

 If this irregular part has any well-marked annual 

 period, such period ought to be apparent on inspection 

 of the converted diagram. In the actual diagrams 

 obtained there seems little or no evidence of the exist- 

 ence of a yearly term. 



W'e now take the second diagram, and by the well- 

 known process construct its hodograph, the curve 

 which gives us a measure of the amount and direction 

 of the force which could have caused the movement 

 recorded in diagram No. 2. This will still be 

 referred to the moving axes, so is not directly avail- 

 able for deducing the true direction of these forces in 

 the earth. Before we can do this we must refer the 

 diagram back again to axes fixed in the earth. Thus, 

 finally, we obtain our diagram No. 4, which 

 may be called the torque diagram, as it represents in 

 direction and relative magnitude the torque or twisting 

 force which has been acting upon the earth to produce 

 the observed movement of the pole. 



The interpretation of such a diagram is a somewhat 

 complex matter, and has not yet advanced far. The 

 causes that seem to be at work producing the irregular 

 shift are either movements of the earth's crust, slow 

 or rapid, as in an earthquake ; the transfer of Arctic 

 ice from one point to another, or its accumulation and 

 disappearance so far as this takes place unsymmetric- 

 ally with respect to the earth's axis ; and possibly 

 extensive barometric changes extending over consider- 

 able areas. 



Of these the transfer of ice is the. largest factor and 

 is probably the one to which most of the irregular 

 polar movement may be ascribed. An earthquake, 

 even of gigantic dimensions, would have an almost 

 negligible etTect. The late Prof. Milne estimated 

 that a very large earthquake might displace ten 

 million cubic miles of earth through a distance of 10 ft. 

 horizontally or vertically. Such a vast cataclysm 

 would only change the position of the pole by a few 

 inches. 



In conclusion it will be an act of natural curiosity 

 to inquire whether there is any evidence of the ampli- 

 tude of these jjolar wanderings having been greater 

 in past times than at present, and whether there is 

 any likelihood of their being greater in the future. 

 To both these questions the answer is " No." The 

 axis of rotation is always kept near the axis of figure 

 by internal friction, and it would require a large 

 change in the distribution of mass to move the axis 

 of figure very far. 



As regards the future, the probabilities point still 

 more strongly in the same direction. Each shrinkage 

 of the earth, whatever its immediate eflfect on the 

 position of the axis of rotation may be, tends ulti- 

 mately to bring it nearer to the axis of figure or prin- 

 cipal axis of inertia, and therefore tends to reduce the 

 average amplitude of the polar path. The distance of 

 the pole of rotation from the mean pole will therefore 

 pradually decrease as the world grows older, while at 

 the same time, as the earth cools and becomes less 

 elastic and more rigid, the rate of rotation will 

 c'uicken. 



NO. 2443, VOL. 97] 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 The Marquess of Crewe has been appointed Presi- 

 dent of the Board of Education, in succession to Mr. 

 Arthur Henderson, resigned. 



The honorary degree of doctor of laws has been con- 

 ferred upon Dr. Otto Klotz, of the Dominion Astro- 

 nomical Observatory, Ottawa, by the University of 

 Pittsburgh. 



Ax explanatory circular respecting the programme 

 for technical schools and classes for the session 1916-17 

 has been issued by the Department of Agriculture and 

 Technical Instruction for Ireland. The regulations 

 which were in operation during the session 1915-16 

 will continue in force with some few alterations, 

 among which we note that a school will not be recog- 

 nised as a technical school under the conditions of 

 section ii. (a) of the programme unless there are at 

 least twenty approved introductor}- and specialised 

 course students in attendance in any session, of w^hom 

 not less than 50 per cent, are specialised course 

 students. Teachers recognised for grants under the 

 conditions of the third paragraph of the explanatory- 

 circular will not be recognised for this purpose as 

 specialised course students. The case of schools of a 

 special character will receive special consideration, 

 and, if it is thought desirable, this regulation may be 

 modified in the case of such schools. Grants will not 

 be paid upon the attendance of a student at more than 

 one lesson in the same syllabus on the same day, 

 unless there is an interval of at least 15 min. between 

 each lesson.' Instruction in the first-year syllabus of 

 a subject of a specialised course will not be permitted 

 to be given concurrently by the same teacher with 

 instruction in any other syllabus or subject. 



A REPORT on Indian education, 1914-15, by Mr. 

 Sharp, educational commissioner with the Govern- 

 ment of India, has recently been received. The ref>ort 

 is a verv brief narrative of the main lines of Indian 

 educational progress, and consists of twentj-seven 

 pages (quarto) of letterpress and fifty-seven pages of 

 tables. In addition, something like fifty interesting 

 illustrations are given of educational buildings of 

 different grades and classes which have been com- 

 pleted during the twelve months under review, and 

 of the arrangements in such buildings. When it is 

 considered that all forms of education are dealt with, 

 from university standards down to primary schools, 

 with an area about fifteen times as large as the 

 United Kingdom, with a number of pupils of between 

 seven and eight millions, and at a cost of eleven 

 crores of rupees (that is, more than 7,200,000/.), it 

 will be understood that a volume of the size mentioned 

 represents almost the utmost limits of condensation. 

 The effects of the war in Europe have been very- dis- 

 tinctlv felt in India, in the first place, in the desir- 

 abilitv for economy, though even here it was found 

 that the expenditure for the year under review was 

 about 90 lakhs (nearly 6oo,oooZ.) higher than in the 

 vear previous to the war. The increase appears to 

 have been mainly due to the rapidly increasing number 

 of pupils in the schools, etc. ; for in the five years up 

 to 19 14 the numbers had increased by no fewer than 

 one and a third million pupils. The war, however, 

 has affected the higher educational institutions more 

 than the lower, for a good many of the British pro- 

 fessors in colleges, etc., are now on military service. 

 It is noticeable that pamphlets, such as '" Why Britain 

 is at War " and others, have been widely distributed 

 in several of the Indian vernaculars to pupils. Also 

 other means, such as lectures, etc., have been taken 



