NA TURE 



\_March 24, 1881 



places and monuments illustrative of various countries. 

 Altogether the work is a really good specimen of its kind. 

 Another volume will bring the story down to the present 

 time. 



LETTERS TO THE EDITOR 



[ The Editor does not hold hwiself responsible for opinions expressed 

 by his correspoitdtnts. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts. No 

 notice is taken of anonymous communications. 

 The Editor urgently requests correspondents to keep their letters as 

 short as possiMe. The pressure on his space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and novel facts, "X 



The Tide Predicter 



I SEE in your last number (p. 467), among the editorial 

 notes, the following: — "Mr. Roberts of the Nautical Almanac 

 office is authorised, by resoluti(3n of Council of the Secretary of 

 State for India, dated August 7, 1880, to make it generally 

 known that his Tide Predicter may bi ejiployed for the pre- 

 paration of Tide Tables for any port for which the requisite data 

 are forthcoming." 



I thiuk it right to call your attention to the fact that the Tide 

 Predicter is in no sense of Mr. Roberts's invention or design. 

 He was employed in 1S73 by me, a^ chairman of the British 

 Association Tidal Committee, to calculate the number of teeth 

 in the wheels of the first Tide Predicter (now the property of 

 the British Association, permanently deposited in South Kensing- 

 ton Museum), and to superintend its construction in London by 

 Messrs. A. Lege and Co. The second Tide Predicter was made 

 for the India Office, according to my advice, by Messrs. A. Lege 

 and Co. of Loudon, under the superintendence of Mr. Roberts. 

 In respect to the plan of the vvheelwork, which is wholly due to 

 Messrs. Lege, it is a copy of the first instrument. It is an 

 improvement on the first instrument in having t\\'enty tidal com- 

 ponents instead of ten, and in having the well-known rigorous 

 method of the slide (Thomson and Tail's "Natural Philosophy," 

 § 55, or " Elements of Natural Philosophy," § 72) for producing 

 simple harmonic motion in a straight line from circular motion, 

 instead of the approximate method of pulleys centred on crank- 

 pins, which for simplicity and economy I used in the first 

 instrument. William Thomson 



The University, Glasgow, March 19 



The Magnetic Storm of 1880, August 

 The Astronomer-Royal has handed to me a copy of the 

 jihotographic record of the variations of magnetic horizontal 

 force as registered at Toronto during the disturbed period of 

 August 1 1 to 14 last. The records of declination and vertical 

 force were imperfect and have not been received. 



The comparison of the Greenwich and Zi-ka-wei (China) curves 

 for the same period (Nature, vol. xxiii. p. 33) indicated that 

 the commencement and end of disturbance (especially the cjm- 

 mencement) occurred nearly simultaneously at both places, and 

 this circumstance is now further corroborated by the Toronto 

 horizontal force curve. 



In what follows, the reference throughout is to Greenwich 

 time. 



The disturbance at Toronto commenced on August 11 at 

 10.20 a.m. At Greenwich (Nature, vol. xxiii. p. 33) it 

 commenced also at 10.20 a.m., and at Zi-ka-wei at I0.l6 a.m. ; 

 at Melbourne (NATURE, vol. xxii. p. 558) it commenced at 

 10.33 '''•™- 



Disturbance ceases at Toronto at about midnight of August 11, 

 and at Greenwich and Zi-ka-wei alsj at about or near midnight, 

 but it dies out more or less gradually, not allowing the limit of 

 disturbance to be always very precisely fixed. 



Sudden motion is again shown (after some hours of quiet) at 

 Toronto on August 12 at 11.40 a.m.; also at Greenwich at 

 1 1.40 a.m. ; some minutes sooner at Zi-ka-wei ; and at Melbourne 

 at about 1 1. 38 a.m. 



Disturbance again dies out more or less gradually at Toronto 

 on August 14 about 7 a.m. ; at Greenwich and Zi-ka-wei at 

 about 6 a.m. ; and at Melbourne at about 7 a.m. 



The commencement of disturbance in the above instances is 

 definite, and the agreement in time, considering the widely- 

 separated geographical position of the four places concerned, is 



noteworthy. The cessation of disturbance is less definite, as has 

 been already remarked, but even here the discordance in time is 

 not very wide. William Ellis 



Royal Observatory, Greenwich, March 12 



Prehistoric Europe 



I MUST adhere to my decision not to play the part of Secutor 

 any further to a glacial Retiarius in the arena of Nature. If his 

 net be strong enough to carry the Upper Pleiocene and the Pleisto- 

 cene mammalia of Europe, as well as Palaeolithic man and the 

 Neolithic sl<ull of Olmo, I wish him joy of them. If, further, 

 he will kindly give me the proof that the mammalia of Auvergne, 

 considered Upper Pleiocene by Falconer, Gaudry, Gervais, and 

 other leading palaeontologists, are, as he terms them, " a hash 

 up," they shall be p'-operly served and iced, if necessary, in my 

 second edition. 



I feel hoNiever that it is only right for me to notice the new 

 gladiator who springs to the aid of his friend. The antiquity of 

 man in the Victoria Cave is solely due, as it appears to me, to 

 the perfcrvidum ingenium (I speak in all respect) of Mr, 

 Tiddeman. It was first based on a fragment of fibula which 

 ultimately turned out to belong to a bear. Then it was shifted to 

 the cuts on two small bones, which were exhibited and discussed 

 at the British Association, at the Anthropological Institute, and 

 at the Geological Society of London. The bones are recent, 

 and belong to sheep or goat, two domestic animals introduced 

 into Britain in the Neolithic age. The cuts have been probably 

 made by a metallic edge. Numerous bones of the same animals, 

 in the same condition and hacked in the same way, occurred in the 

 Romano- British refuse-heap on the top of the clay, and fre- 

 quently slipped do%vn over the working face to the bottom of 

 the cutting befne I resigned the charge of the exploration to 

 Mr. Tiddeman after nearly four years' work. There were frequent 

 slips afterwards. Under these circumstances the reader can 

 decide whether it is more probable that the mutton-bones in 

 question did slip down from a higher level to be picked out at 

 the bottom, or that there is evidence of " interglacial " (J. 

 Geikie) or " preglacial " (Tiddeman) man possessed of domestic 

 animals and probably using edged tools of metal. The mutton- 

 bones seem to me to prove so much on the latter hypothesis, 

 that they may be thrown aside without further thought. 



The reindeer (bones of feet) was found in 1S72 along with fox, 

 rhinoceros, elephant, hyoena, and bison in the cave at the lower 

 horizon, which afterwards was proved to contain the hippopota- 

 mus. It was omitted in Mr. Tiddeman's lists up to 1876, when 

 ] called his attention to the fact. Then he « rote that the fact 

 that it was so found was " noteworthy," and that " the^e remarks 

 [his generalisations] were made solely on the evidence which 

 passed through your present reporter's hands since he undertook 

 to conduct the exploration of the cavern " (Brit. Ass. Rep., 1876, 

 p. I iS). Surely it is too late, in his letter to Nature (March 10, 

 1 88 1), to recall this on the grounds that these remains were 

 discovered in a shaft, that my exploration was not carried on 

 so accurately as his own, and further, that because he did not 

 find the reindeer in the lower strata that I did not. It is not for 

 me to compare my own experience in cave-hunting with his, or 

 to point out the value of negative evidence. The exploration 

 while under my charge was not carrie 1 on by shafts only. When 

 the hyiena-layer was reached it was followed in the deep cutting 

 visited by the British Association in 1873. The presence of 

 reindeer in tlie hyjena-layer renders Mr. Tiddeman's views un- 

 tenable which are based on its assumed absence. Most of these 

 points have been so fully argued out before the above-mentioned 

 societies, that I am sorry to be obliged to repeat them in this 

 letter. W. BovD Dawkins 



Owens College, March 1 1 



Oceanic Phenomenon 

 H.M.'s surveying ship .4/ev-/ was recently engaged in searching 

 for a " shoal " which was reported as existing some 200 miles to 

 the southward of Tongatabu, in the South Pacific. In the course 

 of the survey — which I may add tended to disjirove the existence 

 of any such shoal — it was observed that for several days the sea- 

 surface exhibited large discoloured patches, due to the presence 

 of a fluffy substance of a dull brown colour, and resembling in 

 consistency the vegetable scum commonly seen on the stagnant 

 water of ditches. This matter floated on the surface in irregular 

 streaky patches, and also in finely-divided particles impregnated 



