February 27, 1919J 



NATURE 



51/ 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Sotiei>, Februarj ij. Sir J. J. Thomson, 

 •resident, in the chair.— L. Bairsto« and A. Berry: 

 ["wo-dimensional solutions of Poisson's and Lap 

 equations. Starting from a theorem stated in Lamb's 



Hydrodynamics," problems involving solutions of 

 Poisson's equation are interpreted in terms of the motion 

 11I the conventional inviscid fluid of hydrodynamics. 

 I'lii theorem states thai the continuous acyclii motion 

 of such a fluid ins'iili in outside a rigid boundary can 

 in reproduced by a system of sources round the 

 boundary in all cases for which the fluid is ai rest 



at infinity. The special point of the present papei is 



the formation and solution ol an integral equation in 

 order to find the strength of the sources. The answer 

 appears .1- I integrals which is convergent 



in thi four illustrations given; proof of convergenc; 

 in -the full mathematical sense is not attempted. The 

 method of solution is applicable to boundaries of any 

 shape and to more than one boundary. The integrals 

 are easily obtained by graphical and mechanical 

 methods. Dr. G. II. Thomson: Thi cause of hier- 

 archical order among the correlation coefficients of a 



number of variates taken in pairs. From the ten- 

 dency towards "hierarchical" order among correlation 

 coefficients in mental tests, the conclusion has in the 

 past been drawn that all these correlations are due 

 to the presence of a general factor, and that none of 

 them are due to group-factors which run through two 

 or more tests, but not through all. Although perfect 

 hierarchical order can only be produced in this way, 

 an approximation to perfection can be attained without 

 an) general factor b\ leaving the number and identity 

 of the group and specific factors in each variate to 

 chance. A card experiment is described in which this 

 i- .hull . and specimens of the resulting hierarchies 

 an iu'ven. Tin proof depends on the formula; of 

 Pearson and Filon for the correlation of errors of 

 elation. — Dr. G. V Watson: The transmission of 

 [i waves round the earth. From Austin's experi- 

 mental results it appears thai the magnetic force due 

 to a Hertzian oscillatoi varies as cosec^flexp. (— AA-J0) 

 at angular distance 8 from the oscillator, where A is 

 the wave-length and, in the case of signals over the 

 sea, the. constant A has tin value 96. It seems im- 

 possible to obtain any formula resembling this from 

 a theory of pun- diffraction, and it is therefore neces- 

 sarv to examine the hypothesis (put forward by Heavi- 

 sidi atid uthei~, and submitted to some analytical 

 treatment by Fecles) that the upper regions of the 

 atmosphere act as a reflector of tin waves. It is 

 found that a formula of Austin's type is a consequence 

 of this hypothesis, and that tin numerical value of A 



given by Austin is obtained by assigning suitable 

 values to the conductivity of the reflecting layer and 

 its height abov< th( surfaci "t tin- earth. The problem 

 1 if waves over dry land is also considered and the 

 ,i! iate value of A determined. 

 Geological Society. February 5. Mr. (.. W. 

 Lamplugh, president, in the chair.- Dr. A. Logie 

 Du Toit : The geolog) of tin- Marble Delta I Natal). 

 The papei deals with the crystalline dolomitit marbles 

 ol Pbn Sheiisione (Natal), rocks that have already 

 been the subject of several communications to the 

 : but iis main object is to demonstrate that 

 certain boulders" of alkali-granite, formerh regarded 

 as inclusions, are in reality parts of intrusive tongues, 

 and lo dis, uss the mutual relations of tin igneous 

 rocks and tin adjacent dolomites. 



Linnean Society. Februarj 6. — Sir David Prain, 

 i. nt. in th<- chair. V E. Brown: 111 \ new 

 ..* Lobostemon in the Linnean herbarium; 

 NO. ^574. VOL. I02] 



(.' ' )ld and new species oi Mcscmbryanthcmum, with 

 I remarks. 11) Mr. ('. ('. Laraita, in 1 < p 1 7, being 

 d on a critical revision of Echium, directed 

 the author's attention to a sheet written tip bj Linne 

 a- Echium argenteutn, which upon examination could 

 11 identified with any specimen at Kew or the 

 British Museum. 01 even in herbaria at tin Cape. 

 It is entirely different from Lobostemon argenteus, 

 B 1 . s\n. Echium argenteum, Bergius, with which 

 Linne supposed it to be identical. This single s|>eci- 

 collected at least 147 years ago, does not appear 

 to have be.n found by anj other collectors since that 

 date. The locality given, " moratibus nigris," bj 

 Linne, is Zwartberg, as confirmed bj Governor Tul- 

 bagh's lis! (Proc. L.S., 1917-18, Suppl., p. 10), when 

 it is \o. 145 these figures appearing on the sheet 

 itself, and in the list written up as Echium iruti- 

 eosum, a name abandoned before publication. 12) This 

 paper gave tlie history of the genus Mesembryan- 

 th. inum from the time of Adrian II. Haworth, be- 

 tween 1 71J4 and 1821, who published four monographs 

 of the genus, described mostly from living plants, 

 cultivated bj himself or at Kew. His short descrip- 

 tions are insufficient for identification, but happily a 

 large number of his species are represented by a 

 series of coloured drawings by George Bond and 

 Thomas Duncanson, two artists employed at Kew be- 

 tween 1822 and 184, to make drawings of the plants 

 cultivated there. The result is that many hundreds' 

 of excellent drawings are in existence at Kew, but 

 unpublished and practically unknown, and the atten- 

 tion of botanists is directed to them, about one-fourth 

 ol them being of species of Mesembryanthemum. 



Optical Society, February 14. — Prof. F. J. Cheshire, 

 president, in the chair. — Lord Rayleigh : The possible 

 disturbance of a range-finder by atmospheric refrac- 

 tion due to the motion of the ship which carries it. 

 It was stated that the suggestion had been put for- 

 ward that the action of a range-finder adjusted for a 

 quiescent atmosphere may be liable to disturbance 

 when emplbyed upon a ship in motion, as a result of 

 the variable densities in the air due to such motion 

 and the consequent refraction of the light. The question 

 .ris, s as to the direction and magnitude of the effect, 

 and whether or not it would be negligible in practice. 

 This question was treated mathematical! v in the 

 paper.— L. C. Martin and Mrs. C. H. Griffiths : 

 Deposits on glass surfaces in instruments. The 

 first section of the paper contained a summary 

 of the various phenomena that have been 

 described under the name of "film." In instru- 

 ments deposits occur most frequently on the 

 graticules, and a discussion is given as to the probable 

 ai lion of the lubricants in bringing about the forma- 

 tion of the deposit. The qualities desirable in a 

 lubricant to be used on optical instruments are also 

 enumerated, and a brief summarv is made of the 

 results of hitherto published information on the 

 subject of the deposits. The second section gives .1 



shorl classification of the deposits according to their 

 roscopic appearance, and describes a series ol ex- 

 periments made to test the cause of the formation 

 of the deposit. The experiments were conducted by 

 means of brass nils into which graticule blanks were 

 tilled as windows, these glass surfaces being examined 

 microscopically during the course of the experiments. 



Royal Meteorological Society, February iq. — Sir 



\ ii.ii 1 Shaw, president, in the chair. Dr. S. 

 Chapman: The lunar tide in the earth's atmosphere, 

 lunar tidal variation of barometric pressun lias 

 been well determined at Batavia, from fifty years' 

 hourlv record, and from shortet series ol data, ex- 

 nding over about five years in each case at St. 



