March i, 1888] 



NATURE 



415 



just as are the shore reefs of the neighbouring atoll of Diego 

 Garcia ; but the lagoon contains many knolls abundantly covered 

 with living coral, and there is reason to think that living coral 

 also occurs on the external slopes at Diego Garcia. Unlike 

 Capt. Wharton, I do not consider the favourable conditions for 

 coral growth on the external slopes to be connected with a 

 better food supply, for this would be at variance with the 

 existence of thriving coral patches within the lagoon, which, as 

 I have seen at Diego Garcia, bear no relation to the lagoon 

 mouths, through which food-bearing currents might be supposed 

 to enter to the interior. Indeed, at the last-named atoll some 

 of the most luxuriant coral patches are found at the south end of 

 the lagoon, furthest away from the lagoon outlet. The favour- 

 able conditions are due, I believe, to the action of currents on 

 coral growth. I noticed at Diego Garcia, and Dr. Hickson has 

 made similar observations in the reefs near North Celebes, that 

 corals do not thrive where they are subjected to the direct 

 action of a strong current, nor do they grow in still water, 

 where they are killed by the sand deposited upon them, 

 but they flourish in places where a moderate current flows 

 over them, not so strong as to dash them to pieces, but strong 

 enough to prevent deposition of sand. Such conditions 

 are found everywhere on the external slopes. At the side 

 where a current impinges directly on a slope, the deeper 

 parts of the current strike the slope first, and are in part thrown 

 upwards over the sloping surface, thus moderating the direct 

 force of the more superficial part of the same current. The 

 main part of the current flows tangentially around the obstruc- 

 tion, and thus aff"ords favourable conditions at the sides of the 

 atoll or reef, and finally, on the side furthest from the current, 

 the back-wash causes weak superficial currents which are also 

 highly favourable to coral growth. Thus the coral grows to the 

 greatest advantage around the periphery of a reef, and, as 

 Capt. Wharton says, a ring-shaped reef is the result, and no 

 theory of solution is required to explain the central depression. 



Capt. Wharton states that live coral exists in abundance on 

 the rim of the Tizard Reef. It is not clear whether this means 

 on the external slopes and on the extreme edge of the reef, or on 

 the flat upper surfaces of the reef itself From what I have ob- 

 served at Diego Garcia, it appeare to me hardly probable that 

 the latter can be the case. Coral debris, torn from the corals 

 growing on the slopes, is always carried across those flat surfaces 

 in such quantity as to destroy any living corals upon them. In 

 some cases corals may grow there, but then there are other 

 favourable conditions neutralizing the eftect of the debris. I am 

 hoping soon to publish a full account of my observations at 

 Diego Garcia. G. C. Bourne. 



Anatomical Department, Oxford, February 28. 



Natural Science and the Woolwich Examinations. 



In accordance with Mr. Irving's recommendation, I have 

 carefully considered the letter in the Times from the head 

 master of Clifton College ; but, with all due respect to his 

 distinguished position, I find myself unable to accept his conclu- 

 sions. Men of science will pardon me, if I ask them to examine 

 facts, rather than to follow blindly even the highest authority. 



The obligatory mathematics to be required from candidates 

 for Woolwich are defined as follows in the official regulations, 

 dated December 1887 : — 



"Algebra up to and including the binominal theorem; the 

 theory and use of logarithms ; Euclid, Books i. to iv. and vi. ; 

 plane trigonometry up to and including t'r.e solution triangles ; 

 mensuration ; statics — the equilibrium of forces acting in one 

 plane and of parallel forces, the centre of gravity, the mechanical 

 powers ; dynamics — uniform, uniformly accelerated, and uniform 

 circular motion, falling bodies and projectiles in vacuo. (Ana- 

 lytical methods of solution will not be required.) 



" N.B. — A thorough knowledge of each of the above branches 

 of mathematics will be required. ' 



This amount of mathematics is not beyond the reach of a fairly 

 intelligent lad of seventeen who has been properly taught. 



The inductive process which leads Mr. Irving to denounce so 

 severely my supposed inappreciation of the value of experimental 

 demonstration, laboratory training, and field work is hardly 

 worthy of so eminent a teacher. Although there are good 

 grounds for my opinion that chemistry, physics, and geology, 

 are not good educational subjects for ordinary lads under sixteen, 

 I am entirely consistent in the expression of my regret that the 



War Oflice should have thought it desirable to discourage these 

 sciences. Your able article conclusively proves that these 

 subjects cannot be hastily and superficially learned in such a way 

 as to gain unmerited marks. There are youths with apt in- 

 telligences, quick eyes, and skilful fingers, who ought to be 

 allowed the advantage of their scientific capacity in the Wool- 

 wich competition. But I am unable to see that Mr. Irving's 

 suggestion would do justice to these. A candidate who offered 

 optional mathematics, one language, and two sciences, would be 

 placed at a great disadvantage with those offering optional 

 mathematics, and three languages, both on account of the lower 

 maximum, and also because, with the same relative proficiency, 

 it is so much harder to score in mathematics and experimental 

 sciences and geology than in languages. I therefore respectfully 

 submit that all who have the interests of science at heart should 

 urge that the maximum should be raised to 3000 marks, but I 

 do not think it would be desirable to allow candidates to take 

 more than one subject from Class II., as it would tend to the 

 neglect of more important studies. 

 2 Powis Square. Henry Palin Gurney. 



International Tables. 



I AM instructed by the Meteorological Council to request your 

 insertion of the following notice : — 



The International Meteorological Congres«, which met at 

 Rome in 1879, recommended that a series of international tables 

 should be prepared and issued. 



The work was ultimately intrusted to a Sub-Committee, con- 

 sisting of Prof. Wild and Prof. Mascart. 



The Sub-Committee has prepared a scheme of tables, which 

 has met with a general acceptance among the heads of European 

 meteorological organizations. 



The tables will be in royal quarto, and will cover about 400 

 pages. The price of the work, to be published by Gauthier- 

 Villars, will be 35 francs. 



The Council are requested by the gentlemen who have 

 prepared the tables to ascertain the probable demand for the 

 work in this country, and I am therefore to request through your 

 columns that any intending purchaser will send his name to me. 



Robert H. Scott. 



Meteorological Office, 116 Victoria Street, London, S.W., 

 February 16. 



PLAN OF TABLES. 



CHAPTER II.-Geodetical. 



1. Variation of gravity with latitude and altitude. 



2. Degrees on the meridian. 



3. ,, on circles of latitude. 



4. Duration of sunshine. 



