Dec. 28, 1871] 



NATURE 



175 



Wherever there is an electric current, some heat will be produced 

 and sooner or later radiated into space, so that the comet in each 

 revolution will lose a small portion of its total energy. In the 

 experiments of Arago, Joule, and Foucault, the conversion of 

 mechanical energy into lieat by the motion of a metallic body in 

 the neighbourhood of a magnet was made perfectly manifest. If 

 then there is any magnetic relation whatever between the sua and 

 the comet, the latter will certainly experience resistance. The 

 question is thus resolved into ore concerning the probahili'y that 

 a^coniet would experience electric diit\u-bance in approaching the 

 sun. On this point we have the evidence now existing that there 

 is a close magnetic relation between the sun and planets. If, as 

 is generally believed, the sun-spot periods depend on the motion 

 of the planets, a small fraction of the planetary energy must be 

 expended. I find, indeed, that a very brief remark to this effect 

 was given in the memoir ofthe original discoverers of the relation, 

 namely, Messrs. Warren De La Rue, Balfour Stewart, and B. 

 Loewy. At p. 45 of their Researches on Solar Physics they add 

 a small note to the following effect : " It is, however, a possible 

 inquiry whether these phenomena do not imply a certain loss of 

 motion in the influencing planets." As I conceive, no doubt can 

 exist that periodic disturbances depending upon the motions of 

 bodies must cause a certain dissipation of their energy ; for if 

 stationary the constant radiation of the .sun could not produce any 

 periodic changes, unless the sun were itself variable. Is there 

 not then a reasonable proliability that the light of the aurora 

 represents an almost infinitesimal fraction of the earth's energy, 

 and that in like manner the light of Encke's comet represents a 

 far larger fraction of its energy ? It is also worthy of notice that 

 the tail of a comet is usually developed most largely at those parts 

 of its orbit where the rate of approach or recess is most rapid, 

 and where the electric^isturl>ance would be correspondingly in- 

 tense. I do not, of course, deny that the resisting medium may 

 nevertheless exist, or may by other observations or experiments 

 be made manifest. But I hold that so long as other physical 

 causes can be pointed out which might produce thesame effect, it 

 is quite unphilosophical to resort to a special hypothesis. Encke's 

 comet ought not to be quoted as evidence of the existence of such 

 a medium until electric disturbance is shown by calculation to be 

 insufficient to account for the observed diminution of period. 



Liverpool 



Geological Society, November 14. — Dr. Ricketts, president, 

 in the chair. Mr. T. Mellard Reade, C.E., on the " Geology and 

 Physics of the Post-Glacial Period, as shown in the Deposits 

 and Organic Remains in Lancashire and Cheshire." The paper 

 was largely illustrated by maps and sections. The author's views 

 are summarised in the following conclusions : — I. That siace the 

 glacial period there are distinct evidences in Lancashire and 

 Ciieshire of three periods of depression or downward movement, 

 and two periods of elevation or upward movement. There m.ay 

 also have been a period of elevation and a land surface previous 

 to any of these movements, but posterior to the true glacial 

 times. 2. That the first period of depression, which was the 

 greatest, submerged the land to a minimum of i, 500 feet below 

 its present level — in Wales at least — and was doubtless general. 

 The post-glacial shells of Moel Tryfane and those by the Kibble, 

 indicating ancient beaches, belong to this period. During this 

 time, and the re-emergence of the land, what the author termed 

 the "washed drift sand" was eliminated from, sorted, and 

 reformed out of, the boulder drift, and scattered over the 

 countr)', but has since been much denuded by atmospheric and 

 aqueous or sub-aerial influences above the 25 feet contour, and by 

 sub aerial and submarine denudation below that line. 3. A re- 

 emergence of the land took place, and a land-pause favourable 

 to growth occuned, during which time the "inferior peat and 

 forest beds," or sub-terrene land surfaces, were formed. At the 

 period of pause the land would be higher than now, but the 

 vertical extent of this movement the author purposed investigat- 

 ing hereafter. 4. A second period of subsidence again followed, 

 and a pause occurred at or about the 25 feet contour line. ' ' The 

 Formby and Leasowe marine beds " were now laid down. 5. 

 A second or latest vertical upward movement followed, elevating 

 the Formby and Leasowe marine beds, upon which now grev/ 

 the forest trees, the remains of which assist to form the " superior 

 peat bed " extending along the coast margin from the river 

 Douglas to Bootle in Lancashire, and from the Mersey to the 

 Dee in Cheshire, and remains of which are found as high up the 

 river Mersey as Garston and Warrington. 6. The third or latest 

 downward movement now took place, and during this time the 



river bed at Crossens was silted up, as also the Garston Creek. 

 The drainage was obstructed, and the beds of marine silt inter- 

 calated in the peat. The tidal silt overlying the superior peat 

 bed by the Douglas, the Alt, and the Birket, the silt which over- 

 lay the peat bed of Old Wallasey Pool, and that in which the 

 vertebrre of a whale, now in Brown's Museum, were discovered at 

 the North Docks, and all the deposits to which the author con- 

 fined the term recent, belong to this period, in a pause of which 

 we are now living. 7. That the whole of these movements were 

 uniform over a far more extensive ai'ea than the author has in- 

 vestigated, he has not the shadow of a doubt. That post-glaci.al 

 movements were slow is almost universally admitted, and from 

 these the inference is obvious that the time which they measure 

 compared with the historical period is so vast that it is difficult 

 to form an adequate conception of it. 



Norwich 



Norfolk and Norwich Naturalists' Society, October 31. 

 — Mr. J. E. Taylor read a paper on " The Origin ofthe Norfolk 

 Broads and Meres." With regard to the former, Mr. Taylor 

 propounded the theory that the depressions, so-called, were 

 owing to the inlluence of ice in remote ages, and that the basins 

 thus scooped out had been since filled up by the growth of peat 

 and the soil brought down by floods. His views were supported 

 by an elaborate essay upon tlie probable condition of the Euro- 

 pean continent at the close of the glacial epoch, and the altera- 

 tions effected by "the last geological change in its physical 

 scenery and geography," as illustrated by the deep lakes of 

 " Switzerland, Scotland, Cumberland, &c., hollowed out of the 

 solid rocks by glacier action." He specially referred also to the 

 great similarity in the physical aspect of the Dutch coast as com- 

 pared with the Broad district of our eastern counties. Broads, 

 he remarked, were distinguished from meres by being always in 

 connection with rivers, and having a chalky bottom, more or less 

 filled in with deposits of mud. Meres, on the contrary, in their 

 physical characters, presented an almost entire separation from 

 rivers and streams, "and the fact that they usually lie in the 

 upper boulder clay, and therefore at a considerably higher level 

 than the broads. The water supply of meres was simply the 

 storage of wet seasons." The number of broads on the Biue and 

 its tributaries, amounting in all to twenty-two, as compared with 

 but four on the Vare, he attributed to the former stream having 

 an average breadth of 150 feet, and the latter of only 100 feet. 

 The formation of Diss Mere he considered due to glacial action, 

 " as the neighbourhood abounded in evidences of such pheno- 

 mena." — Mr. J. H. Gurney, jun., exhibited a male specimen of 

 White's Thrush (Orcocincla aiiyca), killed on the loth October 

 last, by Mr, F. Barrett, in a mar.-sh at Hickling, and exhibited by 

 permission of the Rev. J. Micklethwaite, for whose collection it 

 is being preser\'ed by Mr. T. E. Gunn. Mr. Gurney pointed out 

 the distinctions between the closely allied genera of Onvciiich, 

 Tuvdns, and Mtyulu, and made some remarks on 0. auyea as a 

 British species. It is, he said, the Tardus Whitci of Egton, and 

 of YarreU's "British Birds," so called after the well-known 

 naturalist of Selboume, and has been killed in six or seven 

 instances in this country, the specimen exhibited being the first 

 recognised as occurring in this country. It is found in China, 

 and is said to have been met with in Siberia. — Mr. Barrett 

 exhibited specimens of Zvgiznii exiilaiis, a Swedish moth recently 

 taken in Scotland. 



DuiiLiN 



Royal Irish Academy, December 11. — Prof. Hem-y 

 Hennessy, F.R. S., vice-president, in the chair. Prof. Robert 

 S. Ball read two notes on applied mechanics. In the first 

 note it was demonstrated that in whatever manner a figure 

 moves in a plane, a number of points, lying on the circumference 

 of a circle, are any instant in points of inflexion of the curves 

 which they describe, and that the points of the circle are at 

 points the tangent to which meets the curve in four consecutive 

 points. These theorems embrace what are known in mechanics 

 as the parallel motions. The second note contained an elegant 

 geometrical construction by which the consecutive points of con- 

 tact of two curves are determined. — The .Secretary then read a 

 paper by Mr. Hodder M. Westropp, in which the writer stated 

 that he had abandoned his former theory that the Ogham in- 

 scriptions had a Danish origin, and now suggested that after all 

 the leatned interpretations that had been attempted of their 

 meaning, they were nothing more than notches made to mark 

 the number of cattle possessed by the owner of a plot of land at 

 the annual division which took place under the ancient Brehcn 



