•34 ^Iv. \V. Gravatt un the Allunlic Cable. 



All these figures, the sphere excepted, having infinite dimen- 

 sions in certain directions, it follows that amongst the equili- 

 brium-figures of revolution the sphere alone can be realized, in 

 its complete state, with a finite mass of liquid. Accordingly a 

 mass of oil, abandoned freely in the middle of my alcoholic mix- 

 ture, always assumes the spherical form. 



IV. On the Atlantic Cable. By William Gravatt, Esq., 

 F.R.S., F.R.A.S. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



I CONSIDERED this subject, and, as is well known, arrived 

 at my conclusions long ago; and notwithstanding the con- 

 clusions I see were come to at the last meeting of the British 

 Association and at other meetings, and notwithstanding the 

 Astronomer Royal's two papers on the subject, I feel that my 

 original conclusions are unshaken. 



The subject is of great importance, and I will (if you will allow 

 me) give you as brief an abstract of my ideas as I possibly can. 

 I have demonstrated (but without a diagram it is almost im- 

 possible to give the demonstration) that if a vessel be running 

 in a straight course at any uniform speed whatever, and the 

 cable is being paid out over the stern at the same velocity, then, 

 in the case where the strain tending to break the cable as it 

 leaves the stern is just equal to the weight in water of a portion 

 of the same cable, whose length is the depth of the sea, the 

 cable will be at any instant in the same condition as to tension 

 and pressure as if it were simply lying straight on an inclined 

 plane surface immersed in water ; there will be no strain whatever 

 on the particle which happens at any instant to be the bottom 

 particle of the cable, and the cable will therefore sink down in a 

 vertical plane with uniform velocity, and be laid (not stretched) 

 straight along the bottom of the sea without any waste. 

 Let 



« = the angle the cable forms with the horizon. 



/ = the terminal normal velocity in feet per second, or the 



velocity of the cable at right angles to its length. 

 V = the velocity of the ship in feet per second. 

 w = the weight in pounds of one foot of the cable, in water. 

 6?= diameter of the cable in feet. 

 D = the depth of the sea in fathoms. 



L = length in fathoms, from the stern of the ship to where 

 it touches the bottom of the sea. 

 Now the resistance expressed in pounds to each foot in length 



