ISO 



NATURE 



{June 15, i< 



tified with living species when palaeontologists work in 

 unison with naturalists, or when conchologists become 

 acquainted with both kinds of species. This is a great 

 desideratum ; and for want of it several eminent palaeon- 

 tologists (Nyst, Homes, and others) made regrettable 

 mistakes in such identification, having been misled by 

 names and not things. We may observe that Gastro- 

 poden, instead of Gasteropoden, is the more correct and 

 usual spelling of the word. The plates, sixteen altogether, 

 are admirably executed ; and the publication does great 

 credit to the Imperial Institute of Geology at Vienna. 

 J. Gwyn Jeffreys 



LETTERS TO THE EDITOR 

 [The Editor dots not hold himself responsible for opinions expressed 

 by his correspondents. 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 possible. The pressure on his space is so great 

 that it is impossible otherwise to ensure the appearance even 

 >f communications containing interesting and novel /acts.] 



The Winter of 1881-82 



You have given some figures about the winter of 1881-S2 in 

 Great Britain. I t'was relatively much warmer here. The mean 

 temperatures and its variation from average for November, 1SS1, 

 to April, 18S2, was : 



Nov. Dec. Jan. Feb. March. April. 



Mean 320 23^2 295 25^0 31-5 38'2 



Diff. from average + 2 7 +31 + 14-5 +§'4 +S'0 +3'i 



The general character of the e months is thus a very decided 

 high temperature. That of January was the warmest on record 

 in the 130 years' observation. If we take the mean of tbe three 

 months, January, February, and March, it is also the highest on 

 record, viz., 2S7 ; the other years in which these three months 

 had the highest temperature were: 1822, 28.1; 1863, 27^4 ; 

 1843, 26'9 ; 1794, 266. The temperature of the five months, 

 November to March, viz, 2S'2 in 1SS1-S2, was surpassed only 

 once, in 1821-22, 29^3 ; the other years when these months were 

 warmest are: 1S42-43, 276; 1761-69, 27T ; and 182627, 

 26 '9. 



The Neva was frozen less than four months, while on the 

 average the ice lasts nearly live months ^47 days), and in the 

 winter of 1880-S1 the river was frozen 184 days, the longest 

 time on record since the observations began, that is, for about 

 175 years. The date of opening of the river this year, March 30, 

 is the earliest, except that of 1S22 (March 18). 



The last winter is, besides, noticeable for its deficiency of 

 snow, there being scarcely ten days of fair sleighing. The pre- 

 cipitation of the months from November to March was i"9 less 

 than the average, that of December alone by o"'S, that is, by 

 nearly two-thirds. Besides, a large part of it fell as rain. On 

 account of the want of snow, the rivers had not their ordinary 

 spring floods, and great quantities of timber, prepared to be 

 floated for the use of St. Petersburg, could not be moved. 



On the middle and lower Wolga, the snowfall of last winter 

 was excessive, and even Taschkent and the valley of Ferghana, 

 in Central Asia (lat. 40°-42°), had an exceedingly cold winter, 

 with permanent and deep snow. The winter was also very cold 

 in Transcaucasia, the minimum temperature in November, 1881, 

 being lower than ever observed before in Tiflis. 



St. Petersburg, May 27 A. WoElKOF 



The Mean Temperature of the Atmosphere at the 

 Surface of the Earth as Determined by Observa- 

 tions and by Theory 



When several people, not knowing each other, arrive at 

 the same results, the one by compilation and computation of 

 observations, the others by theory, these results present a good 

 probability of correctness, and the theory involved ought to be 

 of interest to science. 



In NATURE, vol. xxv. p. 395, I read — "The temperature of 

 the southern hemisphere has lately been investigated by Dr. 

 Hann with the aid of recent observations of temperature in high 



southern latitudes, especially those made during the Venus transit 

 in 1S74. For mean temperature of the whole atmosphere he 

 obtains I5°'4 C. , and as that of the northern hemisphere was 

 estimated by Ferrel to be I5°'3 C, it is very probable that both 

 hemispheres have the same mean temperature. Dr. Hann, how- 

 ever, also shows that between 40° and 45° south latitude, the 

 southern hemisphere becomes warmer than the northern in the 

 same latitude, and that a difference between the two persists at 

 least to the confines of the hypothetical antarctic continent. ..." 



In "On some Properties of the Earth," 1880 (Wertheimerand 

 Lea, publ.) occur the following passages, founded on and con- 

 nected by theory alone (p. 95): — "We thus find the average 

 temperature of the atmosphere at the surface of the earth to be 

 20° C.| the isotherms of 20° C. having in their mean the parallels 

 of 30° for basis ; this figure, obtained by reasoning, is confirmed 

 by isothermal maps. We will see why the 20° are lowered to 

 I5°'22 C, the true mean temperature of the atmosphere at the 

 surface of the earth." 



And on pp. 123 to 126 : " The line of greatest heat is in the 



mean moved + — of the spkeie, or 3° 58' + 4' latitude, 



2978 175 . 



n rth of the equator. Temperature is therefore in a compressed 

 or higher state in the lower latitudes of the north." . . . 



" Inside the isotherms with the parallels 3S 58' as basis, the 

 temperature of the north is in excess over thit of the south. 

 T his isotherm of the mean atmospheric temperature reaches over 

 sea so far norih as to embrace those seas which may be called 

 the Mediterranean ... it reaches on land to 47" 5°'~3° S^> 

 where the temperature of Genoa in 43° 51' N. lat. is I5°7 *-"•! 

 and that of Alais 44° 10' N. lat. i-. I5°'4 C. Beyond this iso- 

 therm, or beyond the bases of 38 58' lat., the difference between 

 north and south decreases [which implies that the temperature 

 at the south gets gradually warmer than at the north, chiefly in 

 longitudes examined by Dr. Hann]. ... At the isotherms of 

 i°'666 C, of which that at the south is quite maritime, and 

 almost without curving, the equilibrium of temperature between 

 south and north is re-established, the isotherms coincide, each 

 in its mean, in both hemispheres, with their parallels or bases, 

 they divide the hemispheres in proportion I : 478 ..." 



O. Reichenbach 



Sea-shore Alluvion — the "Chesil" 



Greater attention and speculation have been bestowed on 

 this than any other of our marine littoral moles, the Transactions 

 of various societies abounding in papers describing it, and as 

 the westernmost of our south coast beaches, within the limits of 

 the narrow seas, may well terminate a review thereof. 



Leland, Camden, Lambarde, and Holinshed, all describe it, 

 and how it fluctuates in quantity dependent on the wind. Leland 

 used the word "Chesil" (which became a proper name as 

 applied to this particular bank) as a general term, descriptive of 

 shingle banks, throughout his work. Lilly, who wrote in 1715, 

 describes it most accurately. Hutchins calls it "Steepstone," 

 and derives its name from "Ceorl," the Saxon for gravel. 

 Gough adopts the same derivation, calling it "a prodigious heap 

 of pebbles thrown up by the sea, beginning at Chesilton, in 

 Portland, and reaching beyond Swyre, 16J miles." 



The most remarkable feature is the top "full" about fifteen 

 feet above the low er ones at the Portland end forming a huge 

 seaward wall or mole, exceeding anything of the kind to 

 be seen along our coasts, the land-slope of which is flat. At 

 the east end it is thirty to forty feet above high water of springs, 

 gradually lowering westward, and the stones decreasing in size. 

 The land-locked tidal lake, the " Fleet," between it and the 

 main, is another feature so common to these formations ; it ter- 

 minates opposite the valley to Abbotsbury, down which runs a 

 small mill-stream. Between Lord Ilchester's castle and the 

 Abbotsbury Coastguard Station the great beach ceases, the 

 bight terminating in low tertiary cliffs, which intercept the 

 top " full," the lower " fulls " continuing of an average height, 

 as at Deal and el-ewhere ; two to three miles west of Abbots- 

 bury the beach is thrown up into very sharp slopes, which, from 

 the fineness of the mateiial, become very solid, and 'continues to 

 decrease in size and altitude, intercepted by the cliffs at Burton, 

 and again formed into a moderate " full " on each side of Brid- 

 port harbour. The great elevation attained by the eastern end 

 of this bank, where it abuts against the Island of Portland, 

 exhibits an exceptional accumulation of water-driven material 

 in the hollow of, and to the north-east of the Great West Bay, 



