626 



NA TURE 



\CcL 25, 1883 



does not rise nor the liquid fall, and the surface of the liquid 

 disappears." Thus the critical point is the temperature when a 

 liquid and its saturated vapour have the same density. From 

 the experiments of Cagniard-Latour he deduces that at the 

 critical point a liquid has no latent heat, and in summing up he 

 says- "At the critical point there is no difference between a 

 liquid and its vapour, neither in tension, nor density, nor thermal 

 constitution, nor appearance, nor any property by which they 

 can be distinguished." 



Prof H. S. Carhart, of Evanston, 111., has made some 

 researches on the effect on the magnetic field of the rotation of a 

 pierced iron disk in front of the poles of a magnet. The result of 

 this research is that he has found that an iron screen with a hoie 

 in it held in front of the pole of a magnet acts magnetica y, as a 

 screen with a hole in it held near a light acts optically, the 

 shape of the hole being clearly defined; thus showing the 

 difference of intensity of the field when the iron is there and 

 when it is removed. He has made use of this property by 

 placing a small coil capable of inductive action opposite each 

 pole of a horseshoe magnet ; in between the coils and the magnet 

 he rotated a disk of iron with two concentric circles of holes a 

 quarter of an inch in diameter, which came exactly opposite the 

 two poles of the magnet. The inner circle contained thirty-two 

 holes, and the outer contained sixty-four. The two induction 

 bobbins he had connected up with a telephone. W hen the disk 

 was rotated, he distinctly heard two musical notes produced 

 which were an octave apart. The name given to this instrument 

 is the magnetophone. 



Mr E Van her Ven has been making some researches on 

 the use of phosphor hronza and silicon bronze wires for 1 nes the 

 practical re-ults of which are: that their resistances compared 

 with copper of the same diameter are, phosphor bronze, 30 

 per cent. ; silicon bronze, 70 per cent. ; steel being 10-5 per 

 cent. The stretch that can be given from pole to pole is, 

 for steel, 2 mm. diameter, 130 feet ; phosphor bronze or silicon 

 bronze, I mm. diameter, 106 and 91 feet respectively. Another 

 <reat point is that a bronze wire, on account of i's elasticity, 

 would coil up before it had fallen far if broken, thus preventing 

 accidents from broken wires. 



THE GREAT TIDAL WAVE 



WE have received several communications on extra- 

 ordinary tidal phenomena, which seem to be con- 

 nected with the great earthquake disturbance in Java in 

 August last. We bring these communications together 

 here : — 



I have received an interesting letter from Major A. W . 

 Baird, K.E., who directs the Tidal Department of the Survey of 

 India, on the results of the earthquake in Java. The extract 

 from the letter, which I append, speaks For itself. It may be 

 worth mentioning, however, that Negapatam in the Carnatic 

 and Port Blair in the Andaman Islands are nearly in the same 

 latitude and on opposite sides of the Kay of Bengal. It is to be 

 hoped that Major Baird will communicate the results of his 

 investigation to'some scientific society in this country. 



Trin. Coll., Camb., October 18 G. H. Darwin- 



India 

 Extract from a Letter from A. W. Baird to G. If. Darwin, 

 dated Poena, September 27, 1883 

 "The wave caused by the volcanic eruption at Java 

 tinctly traceable on all the tidal diagrams hitherto received, and 

 I am informed of great tidal disturbance at Aden on August 27 ; 

 but the daily reports are always meagre in information. Knrra- 

 chee and Bombay also show the disturbance, and as far as I 

 have examined the wave reached half way up to Calcutta on the 

 Hooghly. ' 



"Negapatam was most disturbed, and at Tort Blair there was 

 very great disturbance. I have reports from Port Blair of tre- 

 mendous noises as if a ship was firing guns as signals of distress, 

 and they sent out a steamer ' mt Similar reports come 



from the Nicobars, and 1 see by the papers the noises were heard 

 at Tavoy and Mergui in Burmah. 



" I am collating the information and getting up diagrams 

 showing the tide curves of August 27 and 2S, all in Port Blair 

 timc and all on the -cale fa I am of opinion that I can dis- 

 tinctly prove the first wave to be negative, and that it certainly ex- 



tended to Negapatam, thus 

 showing that there must have 

 been at first an enormous de- 

 pression or subsidence at the 

 bottom of the sea in the Straits 

 of Sunda. 



" By proper handling of the 

 records I hope to deduce the 

 velocity of the wave from Java 

 to Aden, and from Java up the 

 Bay of Bengal 



" Unfortunately it will take 

 a long time to get the informa- 

 tion about the time the wave 

 w as generated ; but I am leav- 

 ing no stone unturned to get it. 

 I have sent about twenty cir- 

 culars to various port officers, 



and I have asked to 



for information from Batavia.'' 



South Africa 



Some tidal stations have re- 

 cently been established, on my 

 recommendation, along the 

 coast of South Africa, and the 

 results obtained from the ob- 

 servations will .be ultimately 

 discussed. Meanwhile I inclose 

 herewith a tracing from the 

 tidal diagram at one of these 

 staiions (taken at Port Eliza- 

 beth under Mr. Shield, harbour 

 engineer), covering the period 

 from noon on August 26 to 

 noon on August 30. It will be 

 seen from the diagram that till 

 4 p.m. on August 27 the curve 

 was perfectly normal. 



At 8 p.m. on August 27 an 

 extraordinary o dilation, hav- 

 ing a period of about an hour, 

 commenced, and at 9 p.m. had 

 attained a range of five feet. 

 It then gradudly but very 

 slowly subsides. 



Mr. Shield thinks, and I 

 agree with him, that the tidal 

 disturbance in question has its 

 origin probably in the recent 

 disturbance in the Straits of 

 Sunda. Our information here 

 is as yet very defective. Ac- 

 curate data as to that disturb- 

 ance would be of the greatest 

 interest. David Gill 



Royal Observatory, Cape of 

 Good Hope, Sept. 25 



Mauritius 



In the Mauritius Mercantile 

 Record of September 8, Mr. C. 



Meldrum gives a collection ol 

 data on the phenomena ob- 

 served in the neighbor 

 of Mauritius. One 1 f the 1 acal 

 papers, the Progrcs C 

 gave, in its issue of Aug 



mnt of a curious pheno- 

 menon observed in the li 

 of Port Louis, by Capt. Ferrat, 

 f the s.s. Touar/g. The 

 Touareg was moorod in the 

 Trou Fanfaron, near the I 

 Slip. Towards 2 p.m. on 

 August 27 Capt. Ferrat, who 

 was then on board of his 

 vessel, observed that in that 

 I part of the harbojr the sea 







