2ft6 



KNOWLEDGE. 



[December 1, 1899. 



minute cavities, either wholly or in part, of many gems and 

 crystals. A fine sapphire in his collection contained a cavity of 

 a tubular form. This cavity was so regular in its bore that it 

 served the purpose of a natural thermometer. It was a truly 

 microscopical instrument, measuring only one-fourth of an inch 

 in length, and about one-eighteenth of an inch in diameter. On 

 experimenting with this gem it was found that the liquid which 

 half filled the cavity at fifty degrees Fahrenheit, expanded so 

 rapidly that its volume was doubled at eighty-nine degrees 

 Fahrenheit. This increase of bulk within such narrow limits 

 of temperature excluded all ordinary liquids, and on further 

 investigation. Dr. Sorby decided that the liquid was nothing less 

 tlian liquid carbonic acid. 



Problems connected with the tillage of the soil have, hitherto, 

 been looked upon as belonging to the domain of the physicist 

 and chemist. It is only quite recently that it has come to be 

 recognized that the soil teems with myn-iad minute forms of 

 life — useful, harmful, and neutral, and that therefore it is 

 necessary to look for a solution of the problems not to the 

 chemist and physicist alone, but also to the biologist. Soil 

 bacteriology has been engaging the attention of Mr. R. Stewart 

 MacDougall, and in a communication to the Botanical Society 

 of Edinburgh, he briefly summarized the methods that are 

 employed for a microscopic examination of the bacteria con- 

 tained in a sample of any given soil. One gramme of the earth 

 is weighed, placed in a quart of sterilized water, and thoroughly 

 mixed with it by shaking. A gla.5S tube, containing gelatine 

 which has been rendered germ free by repeated heating in a 

 steam bath, is prepared : and the gelatine, when liquefied by a 

 gentle heat, has added to it by means of a sterilized pipette 

 1 c.cm. of the mixture of water and earth. After a thorough 

 mixing, the entire contents are poured out of the tube on to a 

 gelatine plate. In a short time the bacteria begin to grow and 

 multiply by fission, and soon each gives rise to a colony. To 

 get a pure cultivation of a particular species, a small part of a 

 colony is removed with a platinum needle, and is introduced 

 into a fresh gelatine tube. 



NOTES ON COMETS AND METEORS. 



By W. F. Denning, f.r.a.s. 



GlACOBixi's C'OMRT (discovered September 29th) passed its 

 perihelion at the middle of September, and is now receding 

 from both the sun and the earth. At present, the position of 

 the comet is unfavourable, being low in the western sky after 

 .sunset, and the object itself being faint, it will be practically 

 invisible in December even in the largest telescopes. At the 

 lieginning of that month the distance of the comet from the 

 earth will be no less than two hundred and fifty millions of 

 miles. 



Holmes's Comet has been exceedingly faint at its recent 

 return, and will soon pass altogether out of reach. It appears 

 to have been verj- little observed, and it is very fortunate that 

 Messrs. Perrine and Aiken secured a series of observations 

 between June 10th and September 9th. These were obtained 

 with the 36-inch refractor, and are the only ones pulilished, so 

 that it is fair to conclude that some of the other large telescopes 

 failed to show the comet. 



Periodical Comets. — In 1900 the return of several of these 

 interesting bodies will be due. Finlay's comet ought to arrive 

 at perihelion at the end of February, while De Vico-Swift's 

 comet (1844 I. and 1894 II.) is expected in August. Barnard's 

 comet (1884 II.) is due in September. 



Fireball of September 2nd, ]2h. 45M. — A meteor much 

 brighter than Tenus was seen at this time by the writer at 

 Bristol, and by ^Ir. Ivor F. H. C. Gregg at Great Malvern. It 

 left a streak for one minute. At Bristol the path was recorded 

 as from 40° + i'm^ to 37" -^ 74°, while at Great Malvern it was 

 from 15" + 45° to Z-lr>° + 40°. A comparison of the two 

 observations shows that the radiant was at 46°-)- 42", so that 

 the meteor belonged to the a-^ Perseids (" General Catalogue 

 of Radiants," XLIII.). The height of the object at its first 

 appearance was eighty-six miles over Shipston, and at its dis- 

 appearance sixty miles over Tewkesbury. Its earth point was 

 at Aberdare, and its observed length of path twenty-eight miles. 



The meteoric stream from which it was derived has been 

 previously observed as follows : — 



1887, August 30 ... 46°-h43° W. F. D. 



„ September 1-13 ... 45°-t-40° Heis. 



1870 „ 5 ... 48° -^41° Tupman. 



It sometimes furnishes brilliant fireballs. One of the meteors 

 which I recorded from it in 1887, August 30th, was equal to 

 Venus. It appeared at 14h. 27m., and traversed a path of 18i° 

 from 19° -1-27° to 5° + 14°. 



Fireball of October 2nii, 8h. 20m. — This fine object, 

 referred to in last month's Notes, was also seen by Mr. W. S. 

 Price, at Wellington, Somerset. He says it moved with ex- 

 ceptional slowness, even for a meteor travelling from W. to E. 

 Its apparent brightness was scarcely equal to that of Jupiter at 

 opposition, and it exhibited a deep yellow colour. Towards the 

 end of its path it divided into four distinct fragments, all of 

 which moved in the same line. 



Fireball of Octhber 8th, 611. — A splendid meteor wjvs 

 reported as seen at Epsom, West Norwood, Hayward's Heath, 

 and other places. It passed from S.W. across the zenith to N.E. , 

 and its duration of flight was variously estimated as eight, ten, 

 and ten to twelve seconds. Its colour was a glistening primrose 

 yellow, and it left a momentary trail. At Epsom, Mr. W. Nash 

 says he was fortunate in seeing the meteor from the start to the 

 finish, and that it travelled from one horizon to the opposite 

 one. The object was a very interesting one, being evidently 

 derived from a radiant in Scorpio or Libra near the horizon. 

 It must have passed over the English Channel and .South of 

 England, but the descriptions already to hand are not sufficiently 

 definite to enable exact calculations to be made as to its real 

 path in the air. 



THE SHOWER OF LEONIDS IN 1899. 



The expected display has come and gone, and it seems very 

 probable, from the descriptions already to hand, that the meteors 

 have again disappointed expectation. But the weather is in a 

 measure responsible for this, for at many places the nights follow- 

 ing November 14th and 15th were densely overcast. At some 

 stations, however, the sky was partly clear, and a few Leonids 

 were seen in the moonlight, but only in very moderate numbers. 

 A brilliant display, such as that of 1799, 1833 or 1866 was 

 entirely wanting. The following is a summary of some of the 

 reports received : — 



November 10th, 13h. to 15h. 30m., 19 meteors mapped, but 

 no Leonids. — A. S. Her.schel. 



November 10th, lib. 25m. to 14h., 13 meteors mapped, but 

 no Leonids. — W. E. Besley. 



November 10th, 12h. 40m. to 14h. 40m., 13 meteors mapped, 

 but no Leonids. — W. F. D. 



November 10th, 2r, meteors but no Leonids. — T. H. Astbury. 



November 11th, 14h. .30m. to 16h. 3Um., 10 meteors seen, 

 including 2 Leonids.— W. F. D. 



November 12th appears to have been overcast nearly every- 

 where. At Slough, i7h. .30m. to 18h., Prof. Herschel observed 

 2 meteors, one of them a Tjeonid. 



November 13th, I7h. 15m. to 18h., 5 meteors seen, including 

 one Leonid. Sky only one-fifth clear. — W. F. D. 



November 1 4th, 50 Leonids seen in three hours. — Oxford 

 University Observatory. 



November 14th, lOh. 30m. to 18h.,98 meteors (66 Leonids) seen, 

 including a splendid non-Leonid, at 17h. 40m., leaving a train 

 visible for five minutes. — Sir W. J. Herschel. 



November 14th, 13h. 30m. to 14h. 15m., one Leonid seen. — 

 A. S. Herschel. 



November 14th, ]4h. 30m. to 18h., 28 meteors seen, including 

 about 24 Leonids. — R. I. Ryle. 



November 14th, 16h. 3m. to 17h. 53m., 25 Leonids registered, 

 and about a dozen others seen. There was a con.siderable 

 amount of fog. — T. H. Astbury. 



November 15th, 20 meteors seen during the whole night, 

 including 15 Leonids. — Robert Service. 



Reports for the night of Nov. 16th either speak of the over- 

 cast state of the firmament or announce that comparatively few 

 meteors were seen. 



A telegram from New York states that the observers at Van- 

 derbilt University were rewarded with a brilliant meteoric dis- 

 play on the night of Nov. 14th. JNIeteors passed at intervals of 



