4i8 



NATURE 



TNOVEMBER 24, I92I 



British Research on Tides. 



O 



F recent years tidal research in this country has 

 resumed the vigour which it showed during the 

 fruitful years of Sir George Darwin's work and in- 

 fluence. Among oflficial bodies, the Admiralty and 

 Ordnance Survey have shown renewed activity in 

 promoting tidal observation and research ; but" the 

 revival is perhaps most closely linked with the in- 

 terest shown in tidal problems by Mr. G. I. Taylor 

 and by Prof. J. Proudman. The former has made 

 several brilliant incursions into the field of tidal 

 research, and has solved some important out- 

 standing problems. His work on the tidal dis- 

 sipation of energy in the Irish Sea has al- 

 ready inspired other workers to researches of a 

 similar kind. Recently he has published a solu- 

 tion of the problem of tides on a rotating rectangular 

 basin, a subject which had foiled the attempts of 

 many former workers, including the late Lord Ray- 

 leigh; also, by an elegant investigation of the waves 

 in a tapering channel with a sloping bed, he has 

 lately explained the special tidal features in the 

 Bristol Channel. 



Free-lance work of this kind is essential to the 

 progress of tidal theory, but not less necessary is 

 systematic work on the immediate •-'-pctical r->-ohloriiQ 

 of tidal analysis and prediction. The establishment 

 of_ a centre where such work is carried on is due 

 primarily to the second-named mathematician, 

 Prof. Proudman, backed by the University of 

 Liverpool, the docks and "shipping interests in 

 that city, and later by the Department of Scientific 

 and Industrial Research. The , second annual 

 report of the Tidal Institute of the University of 

 Liverpool has just been issued, and describes the 

 work completed or begun, under the direction of 

 Prof. Proudman, during the past vear. A fuller 

 account of some of the work is contained in the 

 report of the British Association Committee appointed 

 "to assist work on the tides"; this report is 

 drawn up by Dr. Doodson, who is the secre- 

 tary both of this committee and of the Tidal 

 Institute. 



The main part of the year's work has consisted in 

 the analysis of tidal observations, partlv from a 

 Liverpool tide-gauge, but chiefly from the Newlyn 

 gauge. Newlyn is one of the four new tidal stations 

 instituted by the Ordnance Survey. The analysis in- 

 dicates that the errors remaining in the predictions 

 made by former methods of harmonic analysis mav 

 amount to more than a foot, apart from the errors 



arising from the use of predicting machines. About 

 half of the error may be due to the inadequate treat- 

 ment of shallow-water effects, while the rest is due 

 to tidal constituents not included in Sir George Dar- 

 win's schedule. A re-examination of the astronomical 

 and dynamical theory of the tides has also been made 

 by Dr. Doodson, who has found a number of terms 

 large enough to demand consideration which are 

 absent from the Darwinian schedule. 



The shallow-water effects have been isolated by 

 successive elimination of known or determined astro- 

 nomical constituents. They show themselves, as 

 theory indicates, in the introduction of components 

 having periods a half, a third, a quarter, and so on, 

 of the primary astronomical components — mainly, of 

 course, of the semidiurnal component. Partly on a 

 basis of theory, and partly as a result of experience 

 with the Newlyn records. Dr. Doodson has formulated 

 a rule connecting the amplitude and phase of these 

 secondary constituents with the resultant semidiurnal 

 tide on any day. The rule is- that the shallow-water 

 constituent of frequency 2« (n = 2, 3, 4) is proportional 

 in amplitude to the corresponding component in the 

 nth power of the resultant semidiurnal tide, while the 

 phases of these two components differ by an amount 

 characteristic (like the factor of proportionality in 

 amplitude) of the station and of the value of n. This 

 rule is valuable because its commercial application is 

 easy ; correction tables for the purpose are readily 

 prepared, since the corrections are functions merely 

 of the time and height of the semidiurnal tide on any 

 given day. 



Much attention has been paid to improved methods 

 of tida! anaivsis and of prediction by the use of the 

 results of such anaivsis. Computational methods are 

 favoured as against mechanical methods ; a test of 

 the accuracy of the tide-predicting machines used by 

 the Admiralty and the India Office has indicated 

 some serious errors in their results, and it is con- 

 cluded that the labour, of reading the curves afforded 

 by the machines, with any pretence to accuracy, is 

 comparable with the labour of direct computation, 

 while the value of the results is greater in the latter 

 case. 



The discussion has so far been confined to the 

 tides of short period, and these still present many 

 unsolved problems. The long-period tides and the 

 meteorological effects also afford an important field 

 for research, which has yet to engage the attention 

 of the committee and institute. 



The Influence of Egypt on African Death Ceremonies. 



AT a meeting of the Royal Anthropological Institute 

 held on October 25, Dr. W. H. R. Rivers, 

 president, in the chair, Mr. T. F. Mcllwraith read a 

 paper on "The Influence of Egypt on African Death 

 Ceremonies." He said that there was strong evi- 

 dence of Egyptian influence in modern Africa, par- 

 ticularly in the region south and west of the Sahara. 

 In West Africa and the Congo preservation of the 

 dead had a wide distribution. The methods employed 

 included desiccation and pressure, frequently assisted 

 by preservatives, such as honey, palm-wine, salt, and 

 spices. Not only were these methods strikingly simi- 

 lar to those practised in Egypt, but there were also 

 resemblances in arbitrary details, such as the plugging 

 of the nostrils, sewing up the opening in the body, 

 placing plates over the mouth and eyes, and , 

 wrapping the corpse in bandages. Equally important 



NO. 2717, VOL. 108] 



was the limitation of the preser\ation of the body 

 to chiefs. Mummification had a slow growth in 

 Egypt under favourable climatic conditions, but it 

 was highlv improbable that similar methods should 

 have been evolved in the humid atmosphere of tropical 

 Africa. 



Coffins and anthropomorphic figures occur widely 

 on the Guinea Coast and in the Congo, and are rare 

 in East Africa. Colflns are usually the prerogatives 

 of chiefs, and often occur in conjunction with some 

 method of preservation of the body. Among the 

 Bacule of the Ivory Coast a representation of the 

 deceased is portrayed on the cover of the coffln, a 

 feature highly suggestive of Egypt. Anthropomorphic 

 figures are employed in a variety of ways in magical 

 and religious ceremonies, and in a few cases are used 

 to house the souls of the deceased, as was done in 



