December 7, 191 1] 



NATURE 



199 



kitanists are justified in ranking this form as a distinct 

 ecies. — B. Hopkinson : A high-speed fatigue tester and 

 e endurance of metals under alternating stresses of high 

 •equency. In this apparatus the test-piece (5" diameter 

 ^ 4" long) is fixed vertically, the lower end being attached 



> heavy masses. The upper end of the piece carries a 

 'eight. The weight is attracted by an electromagnet 

 laced above it and excited by alternating current. The 

 nil thus applied varies periodically between zero and a 

 laximum value, the frequency of the variation being 

 vice that of the current. The test-piece behaves as a 

 >ring, the lower end of which is held fixed, while the 

 pper end carries the weight and is free to move in a 

 srtical direction. The adjustments are such that the 



tural period of vertical oscillations of this system is 

 jproximately equal to the period of the varying magnetic 

 jU, which accordingly sets up large forced oscillations of 

 s own period. By thus using the principle of resonance 

 ith a current frequency of 60 periods per second the 

 mge of pull applied by the magnet may be magnified from 

 ) to 70 times, and the stress produced in the piece can 

 iadily be made to alternate between 20 tons per square 

 ch tension and 20 tons per square inch compression, 

 he number of complete cycles per minute is 7200, and 

 000,000 reversals can be performed in 2\ hours. The 

 st-piece is fitted with a simple form of optical extenso- 

 eter whereby continuous observation can be kept of the 

 lange of length occurring in a cj'cle of stress. From the 

 jange of length the stress can be calculated if the piece 

 approximately perfectly elastic under the stress which 



being applied. An independent estimate of the limits of 

 ress can also be obtained by observing with a microscope 

 le range of movement of the weight and calculating its 

 sceleration from that range on the assumption (the justifi- 

 ition of which is fully discussed in the paper) that the 

 otion is simple harmonic. These two methods of getting 

 :e stress were found to agree closely for the mild steel 

 ied in the experiments up to a range of stress of about 



> tons per square inch. Endurance tests made in the 

 !w machine on mild steel showed that the steel would 

 and at least twenty million cycles of stress covering a 

 inge of 29 tons per square inch. Comparative tests of 

 e same steel made by Dr. Stanton at the National 

 ^ysical Laboratory in a direct-stress testing machine 

 ving about 1 100 reversals per minute showed that at this 

 eed the probable life of the material under the same 

 nge of 29 tons per square inch would be less than 

 0,000 reversals. Similar comparisons with both higher 

 id lower ranges of stress confirmed the conclusion that at 

 e high speed of more than 7000 reversals per minute the 

 idurance is much greater than at iioo reversals per 

 inute, both in the number of cycles and in the actual 

 ne required to produce fracture. 



Royal Meteorological Society, November 15. — Dr. H. N. 



ickson, president, in the chair. — C. Harding: : The 



mormal weather of the past summer. The author pre- 



nted statistics showing the distribution of temperature, 



infall, and sunshine week by week in the various districts 



the British Isles, and also made a comparison of the 



suits with the Greenwich Records back to 1841. From 



e facts thus brought together, Mr. Harding showed that 



far as temperature is concerned the summer of 191 1 was 



ique. The maximum temperature of 100° at Greenwich 



^ August 9 is the highest temperature recorded in the 



ritish Isles since the establishment of comparable ob- 



rvations. The mean temperature for the summer was also 



her than for any similar period during the last seventy 



rs. The maximum temperature of 96° in July has only 



en slightly exceeded on two previous occasions, and the 



tember temperature of 94° has not previously been 



ailed during that month. So many hot days during the 



mmer have never before been recorded. Mr. Harding 



[rther showed that the rainfall for the three summer 



nths has only been smaller in three previous years during 



period of seventy years, and also that the duration of 



[ht sunshine was greater than in any previous summer 



" the introduction of sunshine recorders in 1881. As a 



iqucnce of the exceptional weather the harvest was 



where commenced at an earlier date than usual, and 



quickly concluded under the most favourable conditions. 



NO. 2197, VOL. 88] 



The effects of the drought, other than in relation to the 

 water supply and vegetation, were very far reaching. 

 — ^W. Larden : Observations of solar halos. 



Zooloerical Society, November 21.— Dr. S. F. Harmer, 

 F.R.S., vice-president, in the chair. — Dr. Geoffrey Smith: 

 The fresh-water crayfishes of Australia. The object of 

 this paper was to revise the classification and nomenclature 

 of the Australian and Tasmanian crayfishes, and to give 

 diagnoses of the genera and species with their limits of 

 distribution. The work was based on a large material 

 obtained from all parts of the continent and from 

 Tasmania. Many of the specimens had been collected by 

 the author, but the majority formed a very large collection 

 brought together during the past twenty years by Prof. 

 Baldwin Spencer. F'our genera were recognised, Astacopsis, 

 Cha;rops, Parachasrops, and Engjeus ; the first three genera 

 included the fresh-water crayfishes proper, and the last- 

 named genus contained the land crayfishes, which were not 

 dealt with in this paper. The geographical distribution of 

 these genera and its bearing upon the geographical 

 problems of Australia was discussed, and the view was 

 supported that the Bassian subregion represented the home 

 of the Australian crayfish, and that Astacopsis was nearest 

 the ancestral form. — F. E. Beddard : A new genus of 

 tapeworms from the bustard (Eiipodotis kori). Four com- 

 plete specimens and some fragments of this cestode had 

 been obtained from a South African bustard in the society's 

 gardens, and the author regarded it as a member of the 

 group Tetracotylea, but could not reconcile its characters 

 with those of any other genus of that group at present 

 known. He briefly described its anatomical characters and 

 discussed its systematic position, and proposed a new genus 

 and species for its reception. — A. E. Cameron : The struc- 

 ture of the alimentary canal of the stick-insect, Bacillus 

 rossii, Fabr., with a note on the parthenogenesis of this 

 species. The author stated that this insect had a rather 

 limited distribution, occurring in the south of Europe and 

 in the north of Africa, and that in the wild state it was 

 not found north of Orleans. Certain peculiarities of the 

 alimentary canal were dealt with which were regarded as 

 adaptations to the mode of life of the species. Attention 

 was directed to the fact that the male was only rarely 

 found in the wild state, and that parthenogenetic reproduc- 

 tion of B. rossii had been verified, for during four genera- 

 tions the specimens kept by the author had showed no 

 males. The fact that the males were disappearing sug- 

 gested that parthenogenesis was not the primitive method 

 of reproduction, but that the species had become adapted 

 to it through the failure of sexual reproduction. — H. B. 

 Preston : A collection of terrestrial and fluviatile shells 

 made by Mr. Robin Kemp in British and German East 

 Africa. One new genus and thirty-four new species were 

 described, which represented only a very small portion of 

 the large number of species collected. — G. A. Boulongor : 

 The habits of British frogs and toads. The paper gave 

 information for those who might feel inclined to carry 

 out further observations on the subject of the migrations 

 of Amphibia as dealt with in a paper recently read before 

 the society. The common toad was strongly recommended 

 as the most suitable batrachian on which to institute 

 series of experiments on distant orientation. — R. 

 Lydekker : Milk-dentition of the ratel. The .nuthor 

 described an instance of primitive features present in the 

 milk-dentition being entirely lost in the teeth of the per- 

 manent series. So far as lie was aware, no such atavistic 

 feature had been hitherto recorded in the case of any 

 existing mammals. 



Geological Society, November 22.— Prof. W. W. Watts, 

 F.R.S., president, in the chair.— Prof. T. G. Bonney. 

 F.R.S., and Rev. E. Hill : Petrological notes on 

 Guernsey, Herm, Sark, and Alderney. Further study has 

 been given to the relations of the igneous masses. The old 

 distinction between diorite and syenite cannot be main- 

 tained ; there exists, especially in Guernsey and Alderney, 

 a dioritic magma, which underwent differentiation. The 

 results of this are described, the most basic being found 

 at Fort Albert (Alderney) and Hon Rcpos Bay (Guernsey), 

 and the most acid, which arc really tonalites, in the north- 

 west of the latter island. These and a felspathic variety 



