Jan. 4, 1877] 



NATURE 



199 



round the North Pole also, but less perfectly, and consequently 

 the North Polar barometric depression, though decided, is much 

 less than the South Polar, The reason of this difference I believe 

 to be, that the North Polar cyclone is broken up by local air- 

 currents due to the unequal heating of land and sea — a cause 

 which scarcely exists in the South Polar regions, where almost 

 all is sea or snow-covered land. Joseph John Murphy 



" Towering " of Birds 

 In connection with Mr. Romanes' valuable letter on this sub- 

 ject, the following note may be interesting. Rooks, I am in- 

 formed, are sometimes killed by means of a paper cone containing 

 birdlime, which is placed in a locality where these birds congre- 

 gate. The rook inserts his bill and head into the cone ; after a 

 little time he rises vertically into the air and then' falls dead. 

 My informant — a traveller and sportsman of much experience — 

 considered the upward motion to be due to the obstruction of 

 sight, but the fact, I doubt not, will bear the same explanation 

 as the towering in the case of a wounded grouse. 



Arthur Sutherland 



If it is of any importance to the question I may state that I 

 have seen the following birds "tower '." — common snipe, field- 

 fare, wood-pipeon, pheasant, partridge, common Australian duck 

 {Anas stiperciliosa), large Australian white cockatoo, Australian 

 Nankeen night heron, and Australian piping crow. I have shot 

 many thousands of Australian duck, and towering has occurred 

 among them pretty frequently. In one case, the notes of which 

 ~ have, the duck began to rise almost immediately, and rose to a 

 freat height. I was indoctrinated in the cerebral injury hypo- 

 lesis, but I soon found that this was untenable, for I made a 

 of plucking and examining the heads of all towering birds 

 ?hich I could recover, and there were some among them with 

 wound whatever on the head. One such instance would 

 [have been sufficient to dispose of the hypothesis ; but I was 

 Ptinable to substitute another for it. Tlie explanation given by 

 [r. Romanes meets the conditions as far as they have come 

 my observations. A. N. 



THE SOCIETY OF TELEGRAPH ENGINEERS 



THE Annual General Meeting of this Society was held 

 at The Institution of Civil Engineers, 25, Great 

 George Street, Westminster, on the evening of Wednes- 

 day, the 13th instant. 



The Report submitted by the President and Council 

 showed that during the past year the number of Foreign 

 Members, Members, and Associates had gone on in- 

 creasing until the total of all classes now exceeded 800. 

 Many valuable papers, it was stated, have been sent in, or 

 promised, for discussion during the current session, 

 almost every available evening being already taken up. 

 The result of the ballot for the President, Vice-Presi- 

 dents, and Council for the ensuing year, was announced, 

 Prof. Abel, F.R.S., being elected President. 



A CoHVCf'sazione was held at Willis's Rooms on the even- 

 ing of Monday the 19th inst., when about 600 were present. 

 Amongst these were to be found almost all the prominent 

 members of the telegraphic profession, as well as most of 

 the representatives of the leading cable companies and 

 men whose names are known in connection with electrical 

 or telegraphic engineering. A magnificent display of 

 apparatus had been got together, including everything in 

 the shape of a novelty which had been introduced in con- 

 nection with this branch of science during the past year. 

 Many interesting experiments were shown, and for the 

 more especial gratification of the non-scientific portion of 

 the assembly, Mr. Apps and Mr. Browning of the Strand 

 exhibited respectively their attractive vacuum tubes and 

 microscopical objects. 



Prominent amongst the features of the evening were the 

 experiments designed and personally exhibited by Mr. 

 Robert Sabine. These may be divided into three classes — 

 (i) Showing the circulation of mercury under the influ- 

 ence of oxidation and deoxidation ; (2) Measuring time to 

 the infinitesimal portion of a second ; (3) Showing the 

 potential at various points and the speed of waves of elec- 



tricity through submarine cables. Full descriptions of these 

 experiments — now publicly shown for the first time — have 

 been contributed by Mr. Sabine to the recent numbers of 

 the Philosophical Magazine. It was on the first-named 

 that Sir Charles Wheatstone was engaged at the time of 

 his death in Paris, and, based upon the results which he 

 obtained, he had constructed a form of mercury " relay " 

 constituting one of the most delicate portions of receiving 

 telegraphic apparatus that could possibly be devised. The 

 duration of impact, when an anvil is smartly struck with 

 a hammer, was measured by means of the arrangement 

 in connection with the second series of experiments. A 

 condenser is charged from a potential of one volt, and 

 then discharged through a Thomson's reflecting galvano- 

 meter, the deflection on the scale being noted. The con- 

 denser is again charged ; a hammer in connection with 

 one side of it is then brought on to the anvil which is in 

 connection with the other side ; during the moment of 

 impact partial discharge takes place, the amount of 

 current escaping being known when that which remains 

 is next measured through the galvanometer. All the 

 factors being thus known, the question of the time during 

 which the hammer and anvil were in contact becomes a 

 matter of simple mathematical calculation. The third 

 series, owing to the difficulty of obtaining a sufficient 

 length of Muirhead's artificial cable, was scarcely so suc- 

 cessful as the other two, but yet sufficient was done to 

 show the principle involved. 



Prof. Dewar's electrometer, by means of which the 

 electromotive force of the most minute fraction of any 

 galvanic cell may be measured, and which is based upon 

 the oxidation and deoxidation of mercury, was also 

 shown. 



Amongst the apparatus Sir William Thomson's new 

 form of marine compass proved to be a centre of 

 attraction. The adjusting "spider" — the most recent 

 addition — was absent, but yet enough was exhibited to 

 show that the mariner might to a great extent now render 

 himself independent of solar observations. Eight small 

 magnetic needles are employed, and the friction of the 

 various parts is reduced to a minimum. Two soft iron 

 balls are placed, one on each 'side of the compass, and 

 adjusting rods are employed in addition to them. The 

 liquid gyrostat, already described in Nature, was also 

 amongst Sir William Thompson's collection. 



Hanging around the walls of the room were carefully 

 executed diagrams, showing what are perhaps the most 

 valuable observations'of earth-currents that have ever been 

 made. They were exhibited and are now presented to 

 the Society by Mr. H. Saunders, of the Eastern Telegraph 

 Company. Availing himself of a broken cable between 

 Suez and Aden, Mr. Saunders succeeded in obtaining 

 simultaneous observations at both stations, and saw that 

 they are graphically represented ; the coincidence between 

 the two is striking to a degree. It is to be hoped that so 

 interesting a record as this may be brought prominently 

 forward in the form of a paper, and so elicit a discussion 

 upon a subject which, although occupying the attention 

 of many, still remains one of the most obscure pi-oblems 

 in connection with electrical science. Closely allied to 

 these were the specimens of the movements of the decli- 

 nation and horizontal magnetic force and of the earth- 

 currents as observed at Greenwich and sent up specially 

 for the evening by the Astronomer-Royal. They com- 

 prised the observations for a calm and a disturbed day, 

 and served to show very clearly the correspondence 

 which exists between magnetic and galvanic disturbances. 



A form of grapnel designed by Mr. Andrew Jamieson, 

 assistant to Mr. Saunders, did not fail to attract consider- 

 able attention. The toes, instead of being rigid, are 

 hinged on to a spring which yields under a pressure of 

 two tons, and thus serves to release the toes from any 

 rocks or foreign matter with which it may be brought into 

 contact, whilst a hold is still retained of the cable. 



