50 



NA TURE 



\JMay 17, 1877 



chronicles collected by Pingrc, was first seen early in February, 

 and increasing daily in brilliancy, would appear, if we may 

 rely upon the historians, to have presented a wonderful aspect 

 shortly before Easter. On Palm Sunday, and two following days, 

 we are told "its increase was prodigious ;" "le dinianche, sa 

 queue fut longue de vingt-cinq brasses ; le lundi, de cinquante et 

 meme de cent ; de plus de deux cents le niardi." It then ceased 

 to be visible at night, but during the eight following days it was 

 seen near the sun, which it preceded ; its tail had then shortened 

 to " una ou deux brasses," but its brilliancy was such that the 

 light of the sun did not prevent its being seen at noon-day. It 

 continued visible till the middle of April. 



Some years since the late Mr. John WiUiamr, Assistant-Secre- 

 tary of the Royal Astronomical Society, and author of the valu- 

 able work upon Chinese cometary astronomy, at the request of 

 the writer, made a strict search for mention of a comet or comets 

 in 1402 in several Chinese authorities in his possession, but 

 without any success ; nor is there any reference to a comet in 

 this year in M. Biot's translations. Failing thus to obtain any 

 data for calculation beyond the vague indications of the comet's 

 positions given in the " Cometographie," the writer endeavoured 

 to utilise them to form some idea of the orbit, and found that 

 with perihelion passage assumed on March 21, in longitude 2oS°, 

 ascending node 117°, inclination 55', least distance o'3S, and 

 direct motion, the principal circumstances of the comet's appear- 

 ance, so far at least as regards track across the heavens, mi;;ht be 

 represented ; but its extraordinary brightness is not easily ac- 

 counted for. The comet is mentioned in Kaempfer's Ilislory of 

 Japan, which renders it tlie more curious that the Chinese annals 

 should have no account of it. Struyck thought it was a return 

 of the comet of 1661, but in his day that body was thought to 

 be identical with Apian's comet of 1532, an idea which was 

 negatived by Mechain's subsequent calculations and by tlie non- 

 discovery of the comet about the year 1790, notwithstanding 

 Maskelyne's efforts to insure observations if it returned at that 

 time. 



METEOROLOGICAL NOTES 



V.\RIATIONS IN THE RELATION OF THE BAROMETRIC 



Grapient to the Force of the Wind. — In a very sugges- 

 tive paper recently communicated to the Meteorological Society 

 of London, Mr. Clement Ley shows that the mean velocity of the 

 wind corresponding to each barometric gradient is much higher 

 in summer than in winter, and tliat this is the case at all stations 

 examined, with all winds, with all lengths of radius of isobaric 

 curvature, and with all values of actual barometric pressure. 

 The diurnal and seasonal variation in the relation of the gradient 

 to the force of the wind is unquestionably one of the funda- 

 mental questions of meteorological research, and we hope Mr. 

 Ley will soon again return to its discussion, with ampler data for 

 a more satisfactory handling of the subject than he has yet had 

 before him. That the mean diurnal oscillations of the liarometer 

 cannot be neglected in the inquiry is very evident. Thus, while 

 in June at S a.m. the barometer at Kew is o'Oi5 inch above the 

 dady average, on the coast at Falmouth it is only o'ooi inch ; 

 but while at 3 r.M. it is o'0l5 inch below the average at Kew, 

 it is still O'OOI inch above the average at Falmouth. Crossing 

 to the Continent and contrasting Helder on the coast with Namur 

 inland, it is seen that in June at S a.m. the barometer at Helder 

 is 0'004 inch under the average, while at Namur it is oooS inch 

 above it, but at 3 i-.M. it is at Helder 0007 inch above, whereas 

 at Namur it is o'oi i inch below the average. An interesting part 

 of the paper is that descriptive of the mean diurnal variations in the 

 velocity of the wind, in which, among other interesting fer.tures, 

 it is pointed out that at the coast stations, the mean horary 

 curve in summer approximates in type to the winter curve at the 

 inland stations, the diurnal maximum being about 2 r.M. In 



connection with this it is interesting to note that while at 

 Valentia and Falmouth the anemometric maximum occurs in 

 summer about 2 P.M., the barometric minimum does not occur 

 till from three to four hours later. The point might be even 

 still more strikingly put by a reference to the observations made 

 at Tola, near the head of the Adriatic Sea, where during June, 

 July, and August, 1S76, the anemometric maximum occurred 

 from 10 a.m. to noon, and the barometric maximum from 11 

 A.M. to I P.M. The two maxima are thus all but contempo- 

 raneous, a result directly opposed to the view generally enter- 

 tained that in such cases the barometric maxima are contcmpo- 

 r,aneous with the anemometric minima. London presents very 

 considerable facilities for the working out of this question in iis 

 two well-equipped observatories at Greenwich and Kew, and in 

 the number of meteorological stations situated within a radius 

 of fifty miles, in connection with the Meteorological Office, Mr. 

 Glaisher, and the London Meteorological Society. Observa- 

 tions made at these stations at 9 A.M., 3, and 9 p.m., would 

 render possible the drawing of the isobarics over the south-east 

 of England, with an approach to correctness sufficient to give' 

 the barometric gradients for Greenwich and Kew as may meet 

 the requirements of the problem. Isobarics drawn from the 

 Daily Telegraphic Reports alone, while sufficient in a first ten- 

 tative inquiry, are, owing to the great distances between (he 

 stations, necessarily very hypothetical, and therefore much too 

 rough for any satisfactory investigation of this important subject. 



Climate of Pekin. — A memoir on this subject, read by II. 

 Fritsche before the Imperial Academy of Sciences of St. Peters- 

 burg on August 17, 1S76, has just been published in the Kcpcr- 

 torinm Jiir Mctcoyologtc, The memoir is an able and exhaustive 

 discussion of the elaborate meteorological observations made at 

 Pekin from the beginning of 1841, and published by the Russian 

 Government under the superintendence successively of Kuppfer, 

 Kaemlz, and Wild. H. Fritsche has thus been able to give in a 

 very complete form the hourly and general monthly averages for 

 temperature, pressure, and humidity, and very satis''actory, 

 though necessarily less complete, averages of wind, cloud, rain, 

 snow, hail, and thunderstorms. The mean temperature and 

 pressure of each day of the year has been worked out in detail, 

 and several of the more important extremes .are also tabu- 

 lated. This well-discussed material has a peculiar meteorologi- 

 cal value, arising from the position of Pekin with refer- 

 ence to the continent of Asia, since it resulls from that 

 position that Pekin may be regarded as situated during the 

 winter months in an extensive anti-cyclone, the prevailing winds 

 being from the continent seawards, and from at least April to 

 July, in an extensive cyclone when the prevailing winds blow 

 from the sea in upon the continent. Hence its dry winter climate, 

 the mean monthly rainfall amounting only to o'i4 inch, and its wet 

 summer climate, the average rainfall in July being nearly 20 00 

 inches. Hence also snow falls only on eleven days during the 

 year. Thunderstorms occur on twenty-seven days, from the end 

 of April to the beginning of October, reaching the maximum in 

 June, July, and August, when a thunderstorm occurs on an 

 average about every fifth day. The same season marks the 

 period of hail, which is, however, of rare occurrence, being only 

 once in two years. Of special interest are the hourly averages 

 in their relation to the winds and weather of this part of Asia. 

 Thus, while the climate of Pekin loses much of its continental 

 character during the summer months, the hourly barometric 

 curves lose their strictly continental character, the morning 

 minimum, for instance, falling close to, or even slightly below, 

 the mean of the day, thus tending to be assimilated to the curves 

 of the sea-side climates about the latitude of Pekin. 



Why the Barometer does not always Indicate Real 

 Vertical Pressure.— Mr. Robert Tennent writes from Edin- 



