February lo. 1898J 



NATURE 



347 



side, where its favourite haunts are Labrador and New- 

 foundland, it is still so abundant that many thousands are 

 at times taken by a single vessel. March is the breeding- 

 time, and at this season the young are produced on the 

 ice far away from land. All previous writers with which 

 we are acquainted state that the young are born in the 

 white coat, which is not exchanged for the grey till the 

 lapse of about twelve months. But Commander 

 Robinson is positive that this is incorrect, and that the 

 grey coat is assumed previous to birth. Unfortunately 

 there are no specimens in the British Museum available 

 for deciding this disputed point ; but it is earnestly to be 

 hoped that such may be supplied before long. In the 

 meantime it may be suggested that the discrepancy has 

 arisen from the yoimg of one species having been mis- 

 taken for that of another, although it is at the same time 

 difficult to see how this can have been the case with a 

 seal so peculiar in appearance, and dwelling so much 

 apart as does the present. 



The above are but a few of the leading features in the 

 habits of the northern ice-seals, to describe which in de- 

 tail would require a small volume. Among the points 

 which require special elucidation are what becomes of 

 the great bulk of the harp-seals between their visits to 

 Greenland in May and September, the mode in which 

 sj-als make their breathing-holes, and the colour of the 

 newly-born crested seal. R. L. 



MAGNETIC AND PENDULUM 

 OBSER VA TIONS> 



T T may be remembered that Lieutenant Peary, before 

 ■'• starting on his sixth expedition to Greenland in 

 1896, offered transport on his steamer to two parties of 

 scientific men, and that the opportunity was very properly 

 accepted. The parties — which were under the direction 

 respectively of Prof A. E. Burton, of the Massachusetts 

 Institute of Technology, and Prof. R. S. Tarr, of 

 Cornell University — consisted each of six members, and 

 were entirely independent in organisation and equipment 

 of the main body of the expedition. The researches of 

 the Boston party consist of observations in terrestrial 

 physics, including glacier phenomena, and studies of 

 Eskimo life, and their reports are now coming to hand. 

 The report of Mr. G. R. Putnam, of the United States 

 Coast and Geodetic Survey, who undertook the magnetic 

 and pendulum observations, is now before us. 



Early in July Mr. Putnam left Boston with a complete 

 outfit of magnetic, pendulum, and astronomical instru- 

 ments, and arrived at Halifax, Nova Scotia, two days 

 later. Here he found time to make magnetic determin- 

 ations at the Naval Dockyard, at which station the 

 declination observations cover a period of nearly three 

 centuries. Reaching Sydney, Cape Breton, the starting 

 point of the expedition proper, six days elapsed before 

 the departure of the Hope, Lieutenant Peary's steamer, 

 and in this time all the instruments were set up and 

 used. The voyage along the Labrador coast was only 

 interrupted by a few hours' stop at Turnavik, where 

 magnetic observations were made. Passing up the 

 Hudson Straits, Mr. Putnam spent two days at Ashe 

 Inlet, but here a gale on the second night unfortunately 

 interfered with the full success of his work. The Hope 

 then turned eastward, and on August i the coast of 

 Greenland was sighted. Magnetic observations only 

 were made at Godhavn, and Umanak was reached a day 

 or two after. Here Mr. Putnam's party landed and 

 settled down for a month, while the Hope continued her 

 northern voyage. The required observations having 

 been completed, the whole party indulged in exploring 



1 "The Scientific ^Work of the Boston Party on the Sixth Peary 

 Expedition to Greenland. Report A." 



trips, but on these excursions they could not well take 

 the magnetic instruments. On the return of Lieutenant 

 Peary, the homeward journey began. After the magnetic 

 observations at Godhavn had been repeated, the ship 

 anchored at Niantilik, in Cumberland Sound, where 

 observations were again attempted, but here the value 

 of the pendulum observations was lessened, because 

 unfavourable weather did not allow the necessary time- 

 observations. Sydney was again reached September 26^ 

 and here a few observations were taken, prior to the 

 instruments being shipped to Washington, where they 

 were tested and found to be unaffected by their long 

 journey of 5000 miles. 



The inagnetic outfit, comprising a dip circle of the 

 ordinary Kew pattern and a magnetometer, was lent by 

 the Coast and Geodetic Survey. In the case of the 

 latter instrument, the magnet consisted of a hollow 

 octagonal prism of steel, held in a stirrup with a long 

 arm to which the two silk fibres were attached. By this 

 arrangement the magnet remained sensibly horizontal 

 at ordinary latitudes, but a copper balancing ring was 

 sometimes used at the most northerly stations. The 

 formula used for computing the moment of inertia of 

 this ring (p. 74) is incorrect, and the term \{x^-\-x.^-^ +-*'i^) 

 should be replaced by \{x.^-\-x-^-, although the numerical 

 correction happens to be insensible. For determining 

 the azimuth by the sun, the magnet box is removed from 

 the base and circle, and the latter is then used with a 

 separate theodolite. 



Mr. Putnam's results in this part of his work are both 

 valuable and interesting. Further evidence has been- 

 obtained of the violence of magnetic disturbances in polar 

 regions, although far greater disturbances have been 

 recorded. Thus the range in a day observed at Niantilik 

 exceeded 4^ degrees, a change of over 3 degrees being 

 noticed in twenty minutes. A comparison with the con- 

 temporary record at Washington reveals, it is true, that 

 an unusual magnetic storm visited this city, but its 

 severity as measured by the range of declination was 

 fifteen times less than that at the northern station.. 

 With the exception of Niantilik, earlier information is 

 available with regard to all the stations visited by Mr. 

 Putnam ; and although only Halifax and Godhavn 

 possess satisfactory records extending over the last 

 three-quarters of a century, the general tendency in the 

 change of the magnetic elements seems to be clearly 

 indicated. At present it appears that at all these points- 

 " the westerly declination is diminishing, the northerly 

 dip is diminishing, the horizontal force is increasing, and 

 the total force is diminishing." 



The apparatus used for determining the relative force 

 of gravity, comprised a set of three half-second pendu- 

 lums, one sidereal and two mean time chronometers, and 

 a meridian telescope. The pendulums were swung in an 

 air-tight case, in which the pressure was reduced to about 

 6 cm. by means of an air-pump. All the chronometers 

 were provided with electrical break circuit attachments, 

 and were thus capable of the instantaneous raising of a 

 shutter by an electrical mechanism and the momentary 

 illumination of a slit every second or two seconds. By 

 this means the reflections of a flash in two mirrors, one 

 attached to the fixed knife edge, and the other to the 

 head of the pendulum, could be observed in a telescope. 

 The period of the pendulum was then deduced from the 

 observed coincidences. At the southern stations coin- 

 cidences were observed with sidereal seconds, but nearer 

 the pole, with mean time seconds, on account of the 

 decrease in the period of the pendulum. Whenever the 

 plan could be carried out each pendulum was swung for 

 a period of eight hours, both in reversed and direct 

 positions, and star observations were made at the be- 

 ginning and end of the forty-eight hours. The following 

 table summarises the principal results (p. 103) : — 



NO. 1476, VOL. 57] 



