404 



NATURE 



{August 26, 1880 



and the author has failed to find any excretory organs in their 

 leaves. It may be added, in conclusion, that these organs can 

 excrete not only water but solutions of substances such as tannin, 

 and the juice of Phytolacca berries. Further, Dr. Moll's obser- 

 vations tend to confirm the view that the wood is the channel by 

 which water is conveyed to the leaves from the roots. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, June 17. — "On the Constants of the Cup 

 Anemometer," by the Rev. T. R. Robinson, D.D., F.R.S., &c. 



In a previous paper the author detailed experiments made by 

 attaching anemometers to a whirling machine, and the conclu- 

 sions to which they led. He was however doubtful of the 

 accuracy of the method, and proposed one depending on the 

 action of natural wind. He has tried this, and he thinks success- 

 fully. Two instruments of the Kew type, differing only in 

 friction, were established 22 feet asunder on the roof of the house 

 and 16 feet above it: the number of turns made by each, and 

 the time, were recorded by a chronograph, and from these, v and 

 v, the velocity in miles per hour of the centres of the cups was 

 known. 



The friction of one of these (K) was constant ; that of the 

 other (E) was varied by applying to a disk on its axle Trony's 

 brake, which was connected with a spring balince whose tension 

 was recorded during the time of experiment by a pencil moved 

 by clockwork. Thus the mean friction was obtained. It ranged 

 from 353 grains to 4,982. 



The equation of an anemometer's motion is 



V= -1-1,2 - 2Vi'Ar -/= o 



where V is the unknown velocity of the wind, a and .v two 

 constants which are to be detennined. Each observation gives 

 two equations in which there are four unknown quantities, for it 

 is found that the value of V changes from one instrument 

 to another. This is partly owing to eddies caused by the build- 

 ings, but also in great measure to in'egularity of the wind it?elf. 

 It is however also found that these wind-differences are as 

 likely to have -H as - signs, and therefore it may be expected 

 that their sum will vanish in a large number of observations. 

 The ordinary methods of elimination fail here even to determine 

 with precision a single constant, and he has proceeded by 

 approximation. 



Assuming the value of a given by the actual measurements in 

 his paper = I5'3IS at 30" and 32° for g-inch cups, and that there 

 is no resistance as v- except that in the equation, and assuming 

 an approximate value for x, we can compute V and V. The 

 difference between these must be due to an error in x and to w 

 the wind error, and taking the sum of a series we have 



S(V' - V) -f Sw = A.T X S(« - i') ; e beinr ^ 



f\l ^ 



}" 



If the observations are sufficiently numerous Sot = o, w ith the 

 assumed x -t- Ax thus found, recompute the V till the sum of 

 V - V is insensible, and the final .1- will give V with a high 

 degree of probability. Twenty-one observations gave a value of 

 x considerably larger than what was obtained with the whirling 

 machine, and of course the limiting factor (that when 1/ is so 



large that ■'—; may be neglected). It is for the Kew type 9" cups 



24" arms = 2,831. In this series the differences are so evidently 

 casual as to show that neither a or x change w-ith v. 



With this X, K gives the true value of V at it ; therefore if 

 any other type be substituted for E' it is easy to find its x, for its 

 a is as area of cups, its f is known, and assuming its .i-' and 

 computing as before, we get similarly its A.r. He tried five 

 different types and obtained very unexpected results, for he found 

 that the x varied as some inverse function of the diameter of the 

 cups and of the arms. He gives its values. 

 No. I. Original instrument 12" cups 23*17 arms, .v = i"588o, limit 2"Si2 



.. 2- Kew 9 „ 24, „ I '5919. " 2'S3i 



.1 3- .. 9 .. 12. >. i'7463> .1 3033 



No. 6 is similar to No. 2, and it might be expected that their 

 constants would be equal. The cause of these differences is 

 partly the eddies caused by the cups being more powerful when 



the arras are short, but still more the presence of high powers of 

 the arm and diameter occurring in the expressions of the mean 

 pressures on the concave and convex surfaces of the hemispheres. 

 In the present state of hydrodynamics we cannot assign these 

 expressions, but we know enough to see that such powers may 

 be present. 



As each type of anemometer has its own constants, the author 

 would suggest to meteorologists the propriety of confining them- 

 selves to one or two forms. For fixed instruments he considers 

 the Kew one as good as any, and would wish to see it generally 

 .adopted. For portable ones he has no experience except with 

 Casella's 3" cups 6" arms, which he found very convenient ; he 

 has not however determined its constants. Some selection of 

 the sort seems necessary if it is wished to have an uniform system 

 of wind-measures. 



Entomological Society, August 4. — J. W. Dunning, M.A., 

 F.L.S., vice-president, in the chair. — Sir Sidney Saunders for- 

 warded for exhibition four living specimens of Prosopis riibicoln, 

 all stylopised females recently bred from larvK extracted from 

 briars received from Epiius, and contributed notes thereon. — 

 Jliss E. A. Ormerod exhibited a soft gall-like formation found 

 on Rhododend7-on fcrrugineum, but believed to be of fungoid 

 growth. — Mr. Billups exhibited a specimen of Heptatilacus vil- 

 lostis from Box Hill. — Mr. H. J. Elwes communicated a paper 

 on the genus Colias. — Mr. W. L. Distant read a paper entitled 

 ' ' Notes on Exotic Rhy nchota," with descriptions of new 

 species. j 



Vienna 



Imperial Academy of Sciences, July 8. — The theory of 

 the galvanic element, by Prof. Exner. — Contributions to a know- 

 ledge of the eruptive rocks of the neighbourhood of Schemnitz, 

 by Dr. Hussak. — Action of ammonia on isatin (third part), by 

 Dr. Sommaragua. — On a new hydrocarbon of the camphor 

 group, by Herr Kaehler and Dr. Spitzer. — On china-acid, by 

 Dr. Skraup. — On the influence of concentration of the liquids 

 on the electromotive force of the Daniell element, by Dr. Hep- 

 perger. — On the action of linear current variations on nerves, 

 by Prof. Fleischl. 



July 15. — River-fishes of South America, and other ichthyo- 

 logical contributions, by Dr. Steindachner. — Researches on the 

 influence of light on formation of chlorophyll, with intermittent 

 illumination, by Drs. Mikosch and Stohr. — On the decompo- 

 sition of simple organic combinations by zinc powder (continued), 

 by Dr. Jahn. — Action of mercury-ethyl on iodides of hydrocar- 

 bons, and a new synthesis of acetylene, by Dr. Suida. — On the 

 compounds formed in action of ammonia and water on some 

 chinon-like derivatives of naphtol, by Prof. Ludwig and Dr. 

 Manthner. — Iron oxalate and some of its double salts, by Herr 

 Valenta. — On the decomposition of iron chloride and some 

 organic ferrid salts in light, by Dr. Eder. — On the phenomena 

 in Geissler tubes under external action (second part), by Prof. 

 Reitlinger and Dr. Urbanitzky. — On the isomorphism of rhom- 

 bohedric carbonate and nitrate of sodium, by Hen- Tschermak. 

 — Measurements of crystals of tellurium-silver, by Dr. Eecke. — 

 On the behaviour of some resins in distillation over zinc powder, 

 by Herr Botsch. — On saligenin derivatives, by the same. — On 

 compounds of the pyrrol series, by Dr. Ciamician. 



CONTENTS Page 



Dr. Bastianon THE Brain 3S1 



Letters to the Editor: — 



Eozoic and Pateozoic— Principal J. W. Dawson-, F.R.S. ... 382 



Alga:.— G. F. Chantrell 382 



Lightning Conductors. — Catherine McPherson de Bremon , 382 



Strange Method of Crossing a Torrent.— F. F. Tuckett. ... 382 



Fascination. — Richa rd H odgson .383 



" Hi-per-space." — V — i 383 



The British Association at Swansea 383 



Inaugural Address of Andrew Crombie Ramsay, LL.D., F.R.S., 

 V.P.G.S., Director-General of the Geological Survey of the 

 United Kingdom, and of the JNIuseum o£ Practical Geology, 



President 3S3 



Section C — Geology — Opening Addre?s by H. C. Sorby, LL.D., 



F.R.S.. &c.. President of the Section 390 



Section D^Biology — Opening Address by Dr. A. C. L. G. 



Gunther, M.A., Ph.D., F.R.S., President of the Section . . . 393 



Notes 397 



Our Astronomical Column : — 



The Satellites of Saturn 399 



The Binary-Star o Centauri 399 



The Great Comet of 1880 332 



A Fragment of Primeval Europe. By Prof. Arch. Geikie, 



F.R.S. (With Illustrations) 400 



E.xcketion of Water bv Leaves. By Dr. J. W. Moll .... 403 



Societies and Academies 404 



