October 28, 1909] 



NATURE 



531 



with every possible precision, the improvements made, and 

 yet to be made, are along the line of reduction in time 

 required to achieve the desired result — in other words, 

 towards simplicity. With proper instrumental means and 

 methods it need not require any more time to make 

 iiccurate observations than to get indifferent results with 

 instruments not adapted to the conditions to be met. 



.\s a proof of this is given below the table of results 

 of the work on board the Carnegie from September i to 

 October i8, or in about si.x weeks' time. After the tests 

 in Gardiner's Bay referred to above, the vessel proceeded, 

 under the command of \Vm. J. Peters, to New London, 

 Connecticut, to have some slight alterations made. She 

 left this port on September ii bound for St. John's, 

 arriving there September 25. Here the director rejoined 

 her, having left the vessel in Long Island Sound to attend 

 the meeting of the British Association at Winnipeg, 

 Canada. 



After the necessary shore observations, the Carnegie set 

 sail from St. John's on October 2 direct for Falmouth, 

 England, arriving there on October 14, having had favour- 

 able winds. Owing to the lateness of the season the 

 Hudson Bay cruise for this year had to be abandoned. 



vessel. The installation is in the charge of the chief 

 engineer, .Mr. D. F. Smith, who has had both theoretical, 

 and practical experience with gas engines. Mr. Carl. 

 Smith, an acknowledged gas-engine e.Kpert of the techno- 

 logical branch of the United States Geological Survey, is 

 consulting expert in connection with this work. Should, 

 this type of engine be made a practical success for marine 

 purposes, even though it be but for auxiliary uses, it will 

 be a valuable achievement, being the most economical form. 

 of motor now employed. 



The Magnetic Results. — In submitting now the magnetic 

 results obtained to date, it should be stated that the com- 

 putation and revision of results goes on apace on board with, 

 the observational work, not only that possible errors may 

 quickly be detected, but also that the results may be made 

 known promptly. It is the intention, hereafter, to publish' 

 the results at intervals of about three months. 



Accuracy of Magnetic Results. — In general, the declina- 

 tions given may be taken as correct within o-i°, and only 

 in but a few instances, when the conditions of sea were 

 unusually bad, will the error be 0-2° ; under favourable 

 conditions the observation error in declination with the- 

 marine coUimating compass for the mean result will be^ 



Deck view of the Came^k, showing the chart hcu^e with M.tiinc Cullimalor (A in diagram) in the middle and the two ob,^Li\ato ies. 

 The forward one is uncovered, and inside it position B of the diagram, where the L.C. Dip Circle is mounted; inside the after 

 observatory (the covered one) is mounted the Deflector and Compass (Position C). 



After the completion of the harbour and shore observations ! 

 at Falmouth, the Carnegie, continuing under the command 

 of Mr. Peters, will proceed to Madeira, and will return 

 early next year to New York via Bermuda, the director 

 returning to Washington. 



Personnel. — Besides the director of the department and 

 the commander of the vessel, the scientific and navigation 

 staff is composed as follows : — C. E. Littlefield, sailing 

 master; J. P. .'\ult, E. Kidson, R. R. Tafel, observers; 

 Dr. C. C. Craft, surgeon and observer ; and D. F. Smith, 

 chief engineer. The ship's personnel includes, furthermore, 

 two watch officers, two cooks, eight seamen, and one 

 mechanic. 



■4H.vi7tary Propulsion. — Of considerable interest in marine 

 circles, aside from the magnetic work on board this vessel, 

 are the experiments being made in the perfecting of a 

 producer-gas engine for marine propulsion. Such a plant — 

 and an almost entirely non-magnetic one — is aboard the 

 Carnegie, of 150 horse-power, sufficient to drive her at six 

 knots' speed in calm weather. This engine has already 

 proved a useful adjunct to the vessel's equipment, facili- 

 tating the entering and leaving of ports, and such tests <as 

 were made at Gardiner's Bay requiring swinging of the 



NO. 20S7, VOL. 8j] 



about +005° (see the Gardiner's Bay results). About the- 

 same statement as made for the declination applies to the- 

 dip. The horizontal intensities, as at present given, may 

 be assumed correct within i unit in the third decimal for 

 the severe conditions encountered on the greater part of 

 the cruise thus far ; for fairly good conditions of the seai 

 the error need not be more than 5 in the fourth decimal, 

 and may be made less, as shown by the Gardiner's Bay 

 work. 



In making these preliminary statements, it should be 

 remarked that every possible source of error is considered — 

 in other words, absolute accuracy, not relative accuracy, 

 is meant. For example, when it is declared that, given 

 fairly good conditions, it is possible to get the dip on 

 board the Carnegie within 0-05°, i.e. within three minutes- 

 absolutely, this means more than may at first appear. 

 Thus dip circles — especially ship dip circles — have instru- 

 mental corrections exceeding frequently the relative error 

 of observation. Accordingly, the dip circle on the Carnegie 

 has been compared, not only with various observatory dip 

 circles, but also with an earth inductor at Washington, for 

 the range of dip from -1-88° to -60°. Further control will' 

 be had at the various ports of call during the progress of 



