July 2t5, 1900] 



NA TURE 



307 



transmission of 3'o km. per sec. The agreement of this with 

 the observed rate of transmission of the sensible shock is held to 

 indicate that both are due to a form of wave motion which was 

 propagated at a uniform rate along the surface of the earth. 

 The first two phases, it is suggested, are due to wave motion 

 transmitted through the interior of the earth, and as in the pre- 

 imably isotropic, or nearly so, material of the interior of the 

 trth a separation of condensational and distortional waves 

 .uuld take place, which Knott and Rudzki have shown to be 

 impossible in the rocks of which the surface of the earth is com- 

 posed, it is suggested that these two phases are due to the arrival 

 of the condensational and distortional waves respectively, 

 travelling by brachisto-chronic paths through the interior of the 

 earth. 



This suggestion is followed up in the second paper. The 

 published records of distant earthquakes were looked up, and 

 those selected of which the time and place of origin were 

 known within a limit of error of i minute of time and i minute 

 of arc respectively. Further, on account of the known im- 

 possibility of separation of the two simple forms of elastic wave 

 motion in the surface crust of the earth, only those records were 

 considered which came from a distance of not less than 20° 

 - of arc from the epicentre. 



Seven distinct earthquakes were found of which the published 

 _' records satisfied all these conditions, and as in some of them 

 ' there was more than one shock, they constituted eleven distinct 

 shocks. From the published records were extracted (i) the 

 time of commencement of the record ; (2) the time of any 

 '' sudden increase of movement, when recorded ; and (3) the time 

 ' of maximum displacement. Tabulating these, it is tound that 

 each earthquake exhibits a three-phase character in the record ; 

 /and, further, that if the times are plotted and a curve drawn 

 ' through them, the time curves of the first two phases show pre- 

 ; cisely that curvature which Prof. Rudzki's investigations show 

 to be characteristic of wave motion propagated along brachisto- 

 chronic paths through the earth, where the rate of propagation 

 ' increases with the depth. Continuing these curves by extra- 

 polation to the origin, they give rates of propagation fairly con- 

 cordant with the rates of propagation of condensational and 

 distortional waves as experimentally determined for ordinary 

 ■ rock. As a subsidiary part of this investigation, it is shown that 

 the " preliminary tremors" of earthquakes coming from Japan 

 Vto Europe reach a depth of about "45 of the radius from the 

 surface, attain there a maximum velocity of 14*5 km. per sec. 

 for the condensational, and 8*8 km. per sec. for the distortional 

 wave, and traverse a medium which has, at that point, a bulk 

 modulus of 17 times, and a rigidity of about 21*5 times that of 

 granite. 



The records of the third phase show some irregularity, but 

 the time curve is a straight line, pointing to a uniform rate of 

 transmission along the surface. There is, however, some indic- 

 ation that in the case of the greatest earthquakes it is higher 

 than in the case of lesser ones ; in other words, that the rate of 

 transmission is in some way dependent on the magnitude of the 

 earthquake, hence, probably, on the size of the wave. From 

 this it is concluded that the propagation of these surface undu- 

 lations is, in part at least, gravitational. 



EXPLORATIONS OF THE ''ALBATROSS" IN 



THE PACIFIC.^ 

 AVTE left San Francisco in August of last year, and in latitude 

 31° 10' N., and longitude 125° W., we made our first 

 sounding in 1955 fathoms, about 320 miles from Point Concep- 

 tion, the nearest land. We occupied 26 stations until we reached 

 the northern edge of the plateau from which rise the Marquesas 

 Islands, having run from station No. i, a distance of 3800 miles, 

 in a straight line. 



At station No. 2 the depth had increased to 2368 fathoms, 

 the nearest land, Guadeloupe Island, being about 450 miles, 

 and Point Conception nearly 500 miles, distant. The depth 

 gradually increased to 2628, 2740, 2810, 2881, 3003 and 3088 

 fathoms, the last in lat. 16° 38' N., long. 130' 14' W., the 

 deepest sounding we obtained thus far in the unexplored part 

 of the Pacific through which we were passing. From that point 



1 Abridged from letters written to the Hon. George M. Bowers, U.S. 

 ninissioner of Fish and Fisheries, >Vashington. D.C., by Mr. Alexander 

 i-siz, leader of the expedition of the U.S. Fish Commission Stsamer 

 i.'ross to the Pacific. 



NO. 1604 ^'^L. 62] 



the depths varied from 2883 to 2690 and 2776, diminishing to 

 2583, and gradually passing to 2440, 2463 and 2475 fathoms 

 until off the Marquesas, in lat. 7° 58' S., long. 139° 08' W., the 

 depth became 2287 fathoms. It then passed to 1929, 1802 and 

 104a fathoms in lat. 8° 41' S., long. 139° 46' W., Nukuhiva 

 Island being about 20 miles distant. Bet>veen Nukuhiva and 

 Houa-Houna (UarHuka) Islands we obtained 830 fathoms, arjd 

 5 miles south of Nukuhiva 687 fathoms. When leaving Nuku- 

 hiva for the Paumotus we sounded in 1284 fathoms about 9 

 miles south of that island. These soundings seem to show that 

 this part of the Marquesas rises from a plateau having a depth of 

 2000 fathoms and about 50 irjiles in width, as at station No. 29 

 we sounded in 1932 fathoms. , 



Between the Marquesas and the north-western extremity of 

 the Paumotus we occupied nine stations, the greatest depth on 

 that line being at station No. 31, in lat. 12° 20' S., and long. 

 144° 15' W. The depths varied between 2451 and 2527 fathoms, 

 and diminished to 1208 fathoms off the west end of Ahii, and 

 then to 706 fathoms when about 16 miles N.E. of Avatoru Pass 

 in Rairoa Island. 



Between Makatea and Tahiti we made eight soundings, begin- 

 ning with 1363 fathoms, 2 miles off the southern end of Makatea, 

 passing to 2238, 2363 (the greatest depth on that line), to 2224, 

 1930, 1585, 775, and finally 867 fathoms off Point Venus. 



The deep basin developed by our soundings between lat. 

 24° 30' N., and lat. 6° 25' S., varying in depth from nearly 3100 

 fathoms to a little less than 2500 fathoms, is probably the 

 western extension of a deep basin indicated by two soundings on 

 the charts, to the eastward of our line, in longitudes 125° and 

 120° W., and latitudes 9° and li° N., one of over 3100 fathoms, 

 the other of more than 2550 fathoms, showing this part of the 

 Pacific to be of considerable depth and to form a uniformly 

 deep basin of great extent, continuing westward probably, 

 judging from the soundings, for a long distance. 



I would propose, in accordance with the practice adopted for 

 naming such well-defined basins of the ocean, that this large 

 depression of the Central Pacific, extending for nearly thirty 

 degrees of latitude, be named Moser Basin. 



The character of the bottom of this basin is most interesting. 

 The haul of the trawl made at station No. 2, lat. 28° 23' N., 

 long. 126° 57' W., brought up the bag full of red clay and man- 

 ganese nodules with sharks' teeth and cetacean ear-bones ; and 

 at nearly all our stations we had indications of manganese 

 nodules. At station No. 13, in 2690 fathoms, lat. 9° 57' N., 

 long. 137° 47' W., we again obtained a fine trawl haul of man- 

 ganese nodules and red clay ; there must have been at least 

 enough to fill a 40-gallon barrel. 



The nodules of our first haul were either slabs from 6 to 18 

 inches in length and 4 to 6 inches in thickness, or small nodules 

 ranging in size from that of a walnut to a lentil or less ; while 

 those brought up at station No. 13 consisted mainly of nodules 

 looking like mammillated cannon-balls varying from 4^ to 6 

 inches in diameter, the largest being 6^ inches. We again 

 brought up manganese nodules at the equator in about longitude 

 138° W., and subsequently — until within sight of Tahiti — we 

 occasionally got manganese nodules. 



As had been noticed by Sir John Murray in the Challenger, 

 these manganese nodules occur in a part of the Pacific most 

 distant from continental areas. Our experience has been similar 

 to that of the Challenger, only I am inclined to think that these 

 nodules range over a far greater area of the Central Pacific 

 than had been supposed, and that this peculiar manganese- 

 nodule bottom characterises a great portion of the deep parts 

 of the Central Pacific where it cannot be affected by the deposits 

 of globigerina, pteropods, or telluric ooze ; in the region 

 characterised also by red- clay deposits. For in the track of 

 the great equatorial currents there occur deposits of globigerina 

 ooze in over 2400 fathoms for a distance of over 300 miles in 

 latitude. 



We made a few hauls of the trawl on our way, but owing to 

 the great disiance we had to steam between San Francisco and 

 the Marquesas (3800 miles) we could not, of course, spend 

 much time either in trawling or in making tows at intermediate 

 depths. Still the hauls we made with the trawl were most 

 interesting, and confirmed what other deep-sea expeditions have 

 realised : that at great depths, at considerable distances from 

 land, and away from any great oceanic current, there is com- 

 paratively little animal life to be found. 



The bottom temperatures of the deep (Moser) bisin varied 

 between 34 '6° at 2628 and 2740 fathoms, to 35 "2" at 2440 



