142 



KNOWLEDGE. 



[June, 1903. 



.1. G. Watlihis. — The only satisfactory way to test the 

 magnification of a lens is to project the lines of a stage micro- 

 meter on a screen at, say, ."0 in. distance from the back lens of the 

 objective, measure the separation of lines so projected, and 

 divide by three. 



Seco. — The photographs that you send are exceedingly good, 

 and you have every reason to be satisfied. The iianits of the 

 specimens you wish identified are as follow : — (1) Species of 

 Surirella ; (2 & 4) Anchors and Plates of Synapta ; (3) Actino- 

 cydus ralfsii ; (5 & 6) Wheel plates of Chirodota vinlacea ; 

 (7 & 8) Heliopella metii. The centre specimen is a Radiate 

 plate from .Vijriutroehus rinlcii. 



Communications and enquiries on Microscopical matters are 

 cordially invited, and should be addressed Ui M. I. Cross, 

 Knowledge Office, 326, High Holborn, W.C. 



NOTES ON COMETS AND METEORS. 



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



Present Comets. — There is no tolerably conspicuous comet now 

 visible in the region noitli of the equator. Giacobini's (190) A) is 

 traversing the southern hemisphere, and at the beginning of June will 

 be moving to N.W. in Octans, and in a position about six degrees 

 from the S. pole of tlie heavens. Southern observers will probably 

 have had a good view of this object during April. Early in that 

 month it was about 80 times as bright as when first discovered, but 

 its proximity to the sun at the period named must have prevented its 

 being seen. On April 15tb, however, it was 45° S. of the sun, and a 

 rather striking and conveniently observable object from southern 

 latitudes. 



GiACOBiNi's Comet (1902 b) passed very closely N. of a Geminorum 

 (Castor) at the end of April, but was too faint for ordinary instruments. 

 The iucreasing distance of tliis remote object, situated, as it will be, iu 

 the strong twilight of a June sky, will render it quite invisible. 



GiACOBiNi's Comet (1896 V.). — This faint comet, for wluch Prof. 

 Hus^ey computed a period of 6^ years, is due at perihelion on about 

 June 22nd, and the conditions make it probable that it may be re- 

 deteeted and followed during the ensiung summer and autumn. The 

 preHieted positions of the comet are given in an ephemeris by Ebelli 

 of Kiel, for Berlin mean midnight 



„ 18 ... 

 22 



Juiv 24 ... 



Aui. 25 ... 



Sep. 26 ... 



Oct. 28 ... 



Nov. 20 ... 



Thus, at the opening of June, the object passes 4 degrees S. of 

 7 Pegasi (mag. 3), enters Aries in July, and Taurus iu August, while 

 it will be placed immediately W. of the Hyades in September, 

 thereafter moving very slowly to S.W. T)ie uuit of brightness in 

 above ephemeris corresponds with that exhibited by the onmet when 

 last seen on 1897, January 4. As the date of perihelion is not 

 accurately known, it will be advisible, when sweeping for the comet, 

 to examine the region lying several degrees E. and W. of the positions 

 given in the ephemeris. 



The Apeil Meteoks. — At the period of the recent return of the 

 Lyrids the weather was extremely cold and winterly, with severe 

 frosts and hazy skies at night. Temperature offered a singular 

 contrast to that experienced ten years ago, when summer heat 

 prevailed, the maximum shade readings of a thermometer at Bristol 

 being 1893, April 19,7.5°; April iO, 77°; April 21, 81°; and April 

 22, 78°. The April meteors of 1903 were, perhaps, reguuled with 

 more than usual intere,-t from the circumstance that ju<t 100 years 

 ago (viz., on the morning of 1803. April 20) a briUiant and abundant 

 display of these objects was observed in America. There was, 

 however, no visible repetition of that grand spectacle in the present 

 year, iov on the morning of Ajjril 20 the WTiter, at Bristol, watched 

 a sky that seemed very still; meteors only came at long intervals, 

 while the Lyrids were almost entirely wanting. At lb. 40m. a.m., 

 however, a sudden wave of light caused the observer to look towards 

 I\'.W., when a very brilliant meteor was seen descending slowly from 



Ursie Majoris to Camelopai-di. In travei-sing a path of 39 degrees, 

 it occupied -ii seconds, aud left a thick train of yellow sparks in the 

 immediate wake of its nucleus. b'adiant prohably at 218^ — 31° 

 (about 8° S.W. of 20 Librtc, mag. 3-3'. from which point a well- 

 proncunccd shower of slow meteors was directed at the Lyrid epoi'h 

 in 1900 This fireball may be said to liave fittingly commemorated 

 the centenary of the brilliant display wilnis.^ed in 1803. The :\p il 

 meteors geuerally appear to have presented no special activity or 

 interesting features this voir, but they were pretty well observed, and 

 it is hoped to refer to some of the results next month. 



Large Meteors. — April 11, lib. 56ra. G.M.T.— Fireball brighter 

 than Jupiter obserred at Lisburn, Ireland, by Mr. John McHarg. 

 Kligbt directed from Herculis, or possibly a little higher up, and 

 ended near Cygni. 



April 19, lOh. 6m. — Fine meteor = 9, observed by Prof. A. S. 

 Heischel, at Slough. Path. 217° + 16° to 249° + 35"," and probable 

 radiant at about 172° — 22°. Duration, 3^ seconds. It left a short 

 tail of red flakes. 



April 21, 13h. 11m. — Large meteor, 3x9, recorded by Prof. 

 A. S. Herseliel, at Slough, with a path very swiftly traversed from 

 13U° + 40° to 126J° + 34°. It gave a transient yellow flash, and was 

 directed from the usual radiant of the April Lyrids. 



April 22, lOh. 29m — Meteor = 9, seen bv Mr. C. L. Brook, at 

 Meltham, near Huddersfield. Path, 308° '+ 43° to 345° + 40°. 

 Duration, 3^ seconds. Colour, pale bluish. green. Observed also by 

 Mr. G. W. Middleton, at Mexborough. who says the northern sky 

 was lit up as by a flash of lightning. The fireball seemed to explode 

 at about 6 Cephei and to have been directed from near a Cepbei. 

 After falling 6° or 7° it burst out again with a beautiful greenish light, 

 and expanded into a sort of nebulous halo. 



April 22, lOh. 36m —Meteor = 2t recorded by Mr. T. H. Astbury, 

 at W'allingford, shooting from 203" + 75° to i4()° + 68° in Is sec. 

 It was a fine Lyrid, leaving a brilliant white streak. This meteor was 

 also registered by Prof. A. S. Herseliel. and adi'pting a radiant at 

 271° + 34° from the combined paths, the heights appear to have been 

 from 70 to 56 miles over !Xorthamptonshire. 



THE FACE OF THE SKY FOR JUNE. 



By W. Shackleton, f.e.a.s. 



The Sun. — On the 1st the sun rises at 3.52 and sets at 

 8.3 ; on the 30th he rises at 3.48 and sets at 8.18. 



Summer commences at 3 p.m. on the 22Qd, when the 

 sun enters Cancer ; this is also thelongest day, its duration 

 lieing 16h. 33ni. 



Siinspots are now of freq\ieut occurrence, aud of laj:e the 

 solar disc has scarcely been devoid of spots. 



The Moon : — 



The moon is is apogee on the 13th, and iu perigee on 



the 26th. 



Occultations : — - 



The Planets. — Mercury is unobservahle during the 

 former part of the mouth, since he is in inferior cou- 

 junction witli the sun on the 3rd. Towards the end of 

 the month he is a morning star in Taurus, not far from 

 Aldeharan, and is at greatest western elouyation of 22^ 5' 



