48o 



NATURE 



[September 15, 1904 



appendices, which include an extensive catalogue of 

 the literature on the subject of primaeval man, will be 

 found to contain a large amount of useful information. 



J. E. 



Metallurgia dell' Oro. By Ing. Emilio Cortese. Pp. 



xv + 262; 35 incisioni. (Milano : Ulrico Hoepli, 



1904.) Price 3 lire. 

 Mctalli Preziosi. By Ing. A. Zinone. Pp. xi + 315. 



(Milano: Ulrico Hoepli, 1904.) Price 3 lire. 

 Nothing exactly resembling the Hoepli manuals is 

 published in the English language, though in French 

 the " Encyclopedic scientifique des .'\ide-Memoire " 

 constitutes a close parallel. The Hoepli series now 

 amounts to 800 little volumes dealing with science, 

 literature, and the fine arts. The method of publish- 

 ing is useful, and contrasts favourably with the in- 

 convenient system adopted in the old-fashioned encyclo- 

 paedias with large volumes containing heterogeneous 

 congeries of subjects. The latest additions to the 

 series are neatly bound, well printed with good sized 

 type, and can be carried in the pocket. The book on 

 the metallurgy of gold contains brief accounts of the 

 washing and sluicing of auriferous gravels, and of 

 the crushing and amalgamation of gold ores. There 

 are also chapters on the Plattner and Mears processes 

 of chlorination, on cyaniding, and on the refining and 

 parting of gold bullion. The descriptions are fairly 

 clear and accurate, but some of them deal with anti- 

 quated processes. The Newberj'-Vautin process, the 

 Crauford mill, and Greenwood's electrolytic process 

 are all described, but on the other hand no mention is 

 made of the use of the lead-zinc couple in the precipi- 

 tation of gold from cyanide solutions, or of Taverner's 

 lead-smelting process. In the other book, the metals 

 dealt with are silver, gold, and platinum. The proper- 

 ties of these metals and their alloys, and the methods of 

 assaying and treating their ores are briefly described, 

 and the remaining eighty-five pages of the book are 

 devoted to the uses of gold and silver in the arts. Both 

 volumes are supplied with a complete table of contents, 

 but suffer from the absence of indexes. 



Tlie Telephone Service: its Past, its Present, and its 

 Future. By H. L. Webb. Pp. 118. (London: 

 Whittaker and Co., 1904.) Price 15. net. 

 -Ax interesting description of the general working of 

 the modern city telephone system is given in the pages 

 of this book. No attempt is made to describe the 

 power plant of the modern telephone e.xchange, or the 

 details of other parts of the machinery bv which an 

 efficient telephone service is maintained, but the 

 general principles of this means of communication are 

 clearly explained, and suggested developments of tele- 

 phone policy in Great Britain are discussed. Every 

 subscriber who reads the book will be given an 

 intelligent and tolerant view of the telephone service. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Magnetic Disturbances and Navigation. 

 Can the compasses of modern ships be influenced by 

 magnetic disturbances to such a degree as to imperil navi- 

 gation? The disaster which on the morning of June 28 

 befell the Danish s.s. Norge, and by which about 600 lives 

 were lost, ought, in the opinion of the present writer, to 

 bring this question to the front. The course of the ship 

 should take her about 25 miles south of Rockall. The last 



NO. 1820, VOL. 70] 



observations, by which position, deviation, and the absence 

 of current were ascertained, were made onlv twelve hours 

 before the ship struck, and showed nothing extraordinary. 

 It seems impossible to explain the discrepancy between the 

 real position and that of the reckoning on the morning of 

 June 2.S without assuming a sudden and considerable alter- 

 ation of the deviation on the compass. 



This view is supported by communications, called forth 

 by the disaster, from two captains, who have, or at any 

 rate think they have, directly observed such alterations. 

 The communications run as follows : — 



(i) " A few years ago I (Captain Hveysel, s.s. L. H. Carl) 

 was on a voyage from the United States of America to 

 Denmark, following the great circle from Newfoundland 

 to Pentland Firth, .\bout 200 miles west of Rockall I had 

 the position at noon accurately determined by observations 

 of the sun, but as the sky was clear in the dusk, I deter- 

 mined anew the latitude, as well as the longitude, by stellar 

 observations, and found to my astonishment that the ship 

 had gone forward in a direction about i point more 

 southerly than calculated according to the reckoning. By 

 observation of the pole star it was in fact ascertained that 

 both the compasses of the ship had acquired a hitherto 

 unknown easterly deviation of 10° to 11*^. The weather was 

 fine, but a faint northern light was observed, which I sup- 

 posed to be the cause of the magnetic disturbance. The 

 course was shaped in accordance with the new deviation, 

 but I continued' to take the bearings of the pole star, and 

 towards midnight the compasses were observed to return 

 to their normal deviation, while the aurora disappeared." 



(2) " I, Captain F. W. Horner, master of the s.s. Elixir of 

 West Hartlepool, while on a voyage from Port Inglis, 

 Florida, to Linhamn, Sweden, between noon June 24 and 

 noon June 25, in the vicinity of the Island of Rockall, found 

 by observation of the sun that the deviation on the coinpasses 

 had changed g°, whereby my ship had gone 25 miles out of 

 her course to the north. I was steering to pass 20 miles 

 north of Rockall, and found by observation at noon June 25 

 that I had passed 45 miles north of it. After passing 

 through the Pentland Firth the compasses again returned 

 to normal." 



This last observation has a special interest as relating to 

 the immediate vicinity of Rockall, and to about the same 

 time as the shipwreck of the s.s. Norge. Can any of your 

 readers furnish facts of a similar nature? 



.So far as I have been able to ascertain, disturbances of 

 the declination needle of like duration and intensity are 

 completely unknown, but, to my mind at least, compasses, 

 mounted in steel ships and compensated by powerful 

 magnets, cannot be directly comparable to the needles of a 

 magnetic observatory. Is it possible to explain such 

 temporary deviations of ships' compasses, as appear to have 

 been observed in the cases related above, from the known 

 variations of the earth's magnetism? 



August Krogh. 



The Physiological I.aboratorv, Copenhagen Universitv. 



The Great Red Spot on Jupiter. 



Owing to very ill-health, I have not been able to make 

 observations of Jupiter during the last few weeks, but have 

 been interested in receiving the results of some other 

 observers. It appears that the great red spot is rapidly 

 accelerating its motion, so that its longitude is decreasing, 

 and with a continuation of this behaviour the spot will 

 ultimately correspond with the position of the zero meridian 

 of svstem ii. of Crommelin's ephemerides. The present 

 longitude of the marking is about 25°, which is the same as 

 it was in the summer of 1898, so that the mean period of 

 rotation during the last six years has been identical with 

 the rate of system ii., viz. qh. 55m. 40-635. 



The variations in the velocity of the spot during the past 

 few ^■ears have exhibited a curious oscillation, and it will 

 be important to watch the future developments of the object. 

 It would be interesting to see in N.iTURE during ensuing 

 months some reports froni observers as to whether this 

 singularly durable marking maintains its present rapid 

 westerly drift. W. F. Denning. 



Bristol, .September 12. 



