September 3, 1903] 



NATURE 



AM 



which might influence certain geophysical ihvesti- 

 g^ations, and the fact that alluvium might mask 

 small tremors, are conditions that cannot be avoided. 



In the Beitrdge ziir Geophysik (vi. Band, 3 Heft) 

 issued *' Zur Begriissung der ll. Internationalen Seis- 

 inologischen Konferenz," Prof. Dr. Bruno VVeigand 

 gives an account of the instruments now in use at 

 Strassburg Observatory, and an explanation of the 

 monthiy reports issued from the same. 



The instruments longest in use are two Rebeur- 

 Ehlert horizontal pendulums. In each instrument 

 there are three pendulums arranged at angles of 120° 

 with each other, the idea being that the three records 

 would enable an observer to determine the direction 

 in which an earthquake motion was propagated. 

 Inasmuch as it has been well known for many years 

 past that the movement of the ground as recorded at 

 a given station may be in any azimuth, we are not 

 surprised when Dr. Weigand tells us that no satis- 

 factory result has been obtained. 



The' records are photographic, the source of light 

 and the record receiving surface being at a distance 

 Oi" 5 metres from mirrors on the pendulums. This 

 necessitates the use of powerful electric lamps. This 

 condition, the high sensibility due to high multipli- 

 cation of the instrument, which on certain foundations 

 kads to wandering of the light spot, and the cost of 

 photographic paper, which is run at the rate of 36cm. 

 per hour, preclude the use of this instrument except- 

 ing at a few selected stations. Other instruments are 

 VViechert's astatic pendulum, Vicentini's microseismo- 

 graph, and Onion's conical pendulum, all of which 

 write on smoked paper, Milne's photographic hori- 

 zontal pendulum, which is a type adopted by the British 

 Association, and Schmidt's trifilar gravimeter. 



Brief references to the records of these instruments 

 are published in a Monatsberichte. All that this gives 

 about the Strassburg records of an earthquake is a 

 time for its commencement and its duration as re- 

 corded by a Von Rebeur pendulum. The times of 

 maximum or other phases of motion, amplitudes, 

 periods, and other information required by seismo- 

 logists is omitted. A plus or minus sign indicates 

 whether other instruments did or did not respond to 

 the movement, and the latter signs predominate. 



With the object of showing the superiority of the 

 Strassburg type of instrument, particularly as com- 

 pared with the type adopted by the British .Association, 

 which latter, according to his opinion, should cease 

 to exist. Dr. Weigand emphasises the discrepancies 

 between his various registers. As illustrative of the 

 supposed want of sensibility in the British .Association 

 type, he points out that the Strassburg Circular for 

 August, 1901, shows that the Rebeur pendulum re- 

 corded twenty-four earthquakes, whilst a British 

 Association type, in the same building, only recorded 

 seven. This latter number he now raises to ten. As 

 a matter of fact, seventeen of the Strassburg records 

 correspond with seventeen records obtained in Britain, 

 whilst five entries in the Strassburg list refer to verv 

 small disturbances peculiar to that place, which there- 

 fore may well be regarded as being of doubtful origin. 

 The earthquakes recorded in a given period by the 

 Rebeur and British .Association pendulums were there- 

 fore nineteen and seventeen. Dr. Weigand published 

 these numbers as twenty-four and seven, and similar 

 discrepancies between the records of the Rebeur pen- 

 dulum and the records of all other instruments in use 

 at Strassburg appear in each of the Strassburg 

 registers. 

 J That the Rebeur pendulums as installed at Strass- 



burg have a higher sensibility than othier seismographs 

 is well known, but it must not be overlooked that this 

 high sensibility is one factor which prevents their 

 NO. 1766, VOL. 68] 



general adoption. That the British Association type 

 of instrument is sufficient for the purposes for which 

 it was intended is amply shown in the reports issued 

 by the Association. Experiments are now in progress 

 to increase the speed of the record receiving surface 

 connected with this apparatus about four times, and 

 to reduce the cost of photographic material to about 

 3^. per annum. It now costs 61. los. per annum, 

 whilst paper for the Rebeur apparatus costs 15^ 



When Dr. Weigand complains of the want of sharp- 

 ness in the trace yielded by the British Association 

 instrument, he should evidently look to its adjust- 

 ments, for it is its pronounced sharpness that compen- 

 sates for its want of multiplication. In this respect 

 the records it yields are far superior to those obtained 

 from any other form of photographically recording 

 seismograph. 



That it should be affected like other instruments 

 with so-called " Mikroseismische Unrulie " is what 

 might be expected if located in a cellar, 



.Altogether, the institute at Strassburg as " der Kais. 

 Hauptstation " might easily be improved, whilst if its 

 publications took the form of the excellent registers 

 issued in the Bollcttino della Societa Sismologica 

 Italiana, they would be of greater value to working 

 seismologists. ..• 



THE INTERNATIONAL STUDY OF THE SEA.' 



THE publications mentioned below are the first 

 reports of the International Council for the Study 

 of the Sea which was constituted by the meeting ot 

 representatives of the maritime Powers of northern 

 Europe at Christiania in 1901, and now has its seat at 

 Copenhagen. The bulletins deal with what has come 

 to be known as hydrographic work carried out on the 

 quarterly cruises, in which special ships of each of the 

 participating States take part. The word hydrography 

 is not, however, used in the sense made tamiliar by 

 the hydrographic offices of the various Admiralties ; 

 it means, if we may borrow for a moment the termin- 

 ology of chemistry, scarcely more than inorganic 

 oceanography. We say scarcely more, for in these 

 bulletins it does include the study of the distribution of 

 plankton, but for this purpose plankton are treated 

 rather as current-floats than as organisms. 



It will be remembered that the International Council 

 was formally constituted at a conference held at 

 Copenhagen in July, 1902, and that no time was lost 

 in getting to work is plain from the fact that the first 

 number of the Bulletin deals with a series of cruises in 

 August, 1902, the second with a similar series in 

 November or December, 1902, and the third with 

 February, 1903. These cruises have since been con- 

 tinued quarterly, and we understand that they 

 are now more complete, and the results obtained 

 more readily comparable than was possible when the 

 collaboration was only beginning. Viewed from tne 

 standpoint of scientific efticiency, the work of the 

 Council is hampered by the very short term for which 

 the various Governments have granted the necessary 

 funds and the stringent conditions as to endeavouring 

 to obtain practical results directly beneficial to fisheries 

 which have been insisted on in some cases. But there 

 is reason to hope that these very difficulties will act 

 as a spur. 



The bulletins are mere records of observations, they 

 contain a minimum of explanatory letterpress, and no 

 discussion at all. It might be found desirable to print 



1 Conseil permanent international pour rExploration de la Mer. Bulletin 

 des V<e>ultat.s acqnis pendant l<-s coiir es p^riodique<. Public par le Bureau 

 du Conseil avec I'assistance de M. Knudsen, Charge du .Strvice Hydr. - 

 graphiqu^ Annie 1903-1903. Nts. i, jet 3. (Copenhague : A. F. H6st 

 et Kils, 1903.) 



