B^EITISH ASSOCIATION FOR THE ADVANCEMENT OF SClElSrCE. 30 



Tlie Athenceum reporter, from whose notes we derive the above abstract, re- 

 Tsports the foUowiag interesting discussion in the Section, to which it gav« 

 ■rise :— 



Ms*. James Thomson did not conciir in the view taken by the author, as he con- 

 ceived that in tbe method he proposed the cabk would be apt to sink in festoons: 

 a bend when once formed by its superior weight dragging down more rapidly 

 t'han the parts on each side, yet horizontal, and thus tbe cable would have large 

 folds, or even coils, when it reached the bottom. 



During the conversation which arose in the Section after the reading of this 

 €ommunication, a new light seemed to break upon the members, as it seemed to be 

 universally admitted that it was mathematically impossible, unless the speed of 

 the vessel from which the cable was payed out could be almost infinitely increased, 

 to lay out a cable in deep water (say two miles or more) in such a way as not to 

 require a length much greater than that of the actual distance, as from the inclined 

 direction of the yet sinking part of the cable, the successive portions payed out 

 must, when they reached the bottom, arrange themselves in wavy folds ; since tbe 

 actual length is great-er than the entire horizontal distance. The fact, therefore, 

 which, when noticed, led to the increasing of the strain on the Atlantic cable un- 

 til it broke, ought to have been anticipated, and must be provided for in the future 

 progress of that great national undertaking. 



ON THE AMOUNT AND FEEQtTENCT OF TEE MAGNETIC DISTURBANCKS, AND OF THE 

 AURORA AT POINT BARROW, ON THE SHORES OF THE POLAR SEA. — BY MAJ^E- 

 GENERAL SABINE, 



Point Barrow is the most northern cape of that part of the American continent 

 which lies between Behring's Strait and the Mackenzie River. It was the statioa 

 of H.M.S. Plover from the summer of 1852 to the summer of 1854, and to 

 Captain Maguire, now in the Section, and the officers of that ship, they were indebted 

 for the very valuable series of observations which he was now about to lay before 

 the Section, and in part discuss. They were furnished with supplies of provisions, 

 tfec, for Sir John Franklin's ships, had theysucceededinmaking their way through 

 the land-locked and ice-encumbeved channel, through which they sought to effect 

 a passage from the Atlantic to the Pacific. In this most dreary and otherwise im- 

 interesting abode, Capt. Maguire and his ofiicers happily found occupation during 

 seventeen months, unremittingly, in observing and recording every hour the var- 

 iations of the magnetic and concomitant natural phenomena, in a locality perhaps 

 one of the most important on the globe for such investigations, Their observatory, 

 placed on the sand of the shore, which for a long tract nowhere rose much above 

 five feet above the sea, was constructed of slabs of ice, and lined with seal-skins 

 throughout. The instruments had been supplied by the "Woolwich establishment, 

 with the requisite instructions for their use ; and the observations were made and 

 recorded precisely in the same manner as those of the Colonial magnetic observa- 

 tories. These were sent by Captain Maguire to the Admiralty, and were in due 

 course transmitted to General Sabine, by whom they were subjected to the same 

 processes of reduction as those made in the Colonial observatories. The author 

 then exhibited to the Section six long rolls, containing the results of this discussion, 

 giving the reduced observations at each of the hours of the twenty-four. A suffi- 

 cient body of tbe larger disturbances having been separated from the rest, it was 



