94 



KNOWLEDGE. 



[Apbtl 1, 1901. 



the new condenser introduced liy !Mr. C. Baker, of '^44, High 

 Holborn : in this a specially large field lens is provided; the 

 ])OWer (Tsi°-) '^ exactly the right one for histologists and workers 

 with medium power objectives, while the aplanatic aperture 

 closely approaches -W. We have found it most effective in 

 some work we have been doing recently, and great credit is due 

 to the maker for its introduction. 



The worker who does not go beyond an aperture of 1-25 can 

 do all that his lens will permit with a dry condenser having the 

 nominal aperture of 1-0 and yielding an aplanatic cone of 90 as 

 several of them do. If higher a])ertures are used, an oil immer- 

 sion condenser is necessary. This advice has an appalling 

 ^ound. but it is too little recognised that such systems can 

 usually be worked dry, and will then give an aplanatic cone 

 exceeding -B''. Such is the ca.se with Watson & Sons' holoscopic 

 condenser. Again, the top lens can be removed and a condenser 

 of low power secured. Oil immersion condensers are too little 

 appreciated, and it will be found, if it is desired to work with 

 medium and high powers, that the oil immersion system will 

 serve every purpose and is practically a universal condenser. 



The QrEKETT Microscopical Club.— The practical work 

 done by this Society, which was founded in the year ISfi.'i, is 

 recognised as being of the first importance. 



The meetings are attended by the foremost microscopists of 

 the day. The journal, which is published bi-annually, and gives 

 reports of the papers read and the proceedings generally of the 

 club, is always worthy of careful perusal, but the great charac- 

 teristic feature of the club is the welcome it extends to the 

 amateur microscopist and the means it affords for bringing the 

 novice into touch with the sound principles of manipulation, 

 working and collecting. 



On the first Friday in each month, a " Gossip' evening is 

 held, at which specimens are exhibited by members and dis- 

 cussed conversationally, the regular business meetings of the 

 society taking place on the third Friday in each month. There 

 is, in addition, a first-rate library, and cabinet containing 6000 

 slides, which are at the disposal of the members. 



"We have before us a list of the excursions for the forth- 

 coming season. These take place principally on Saturday 

 afternoons, and have for their object the collecting of material 

 that will afford interesting studies microscopically. "Pond 

 life " has always been a very strong subject with the club. 



Visits are cordially invited to the meetings, which are held at 

 20, Hanover Square. 



When it is stated that all these advantages are offered without 

 entrance fee for the modest sum of 10s. per annum, it will be 

 conceded that every microscopist ought to make a point of 

 becoming a member, and so supporting, in a practical manner, a 

 club which has in the past and will continue in the future to 

 jiromote the best interests of every feature in microscopy. 



Communications on the subject of membership should be 

 addressed to the Hon. Secretarv, G. C. Karop, Esq., m.r.c.s., 

 198, Holland Road, W^., or to the Hon. Editor, D. J. Scour- 

 field, Esq., F.R.M.S., 03, Queen's Road, Leytonstone. 



We hope, as the season advances, to give short reports of the 

 excursions of the Qnekett Club members, giving details of the 

 material that is collected and the place where it is found. 



RiNOiNO Slides. —Many amateurs prepare and mount speci- 

 mens remarkably well, but few manage to put the ring of 

 cement on neatly. It requires practice certainly, but generally 

 it is through using the cement in too thick a condition. Pro- 

 fessional mounters have two bottles, one containing the cement, 

 the other the solvent — generally turpentine or methylated 

 spirits. The brush is first dipped in the solvent, then in the 

 cement, and a thin coat is deposited on the slide as it is rotated 

 on the turntable. Some build the ring up at once, others allow 

 the first layer to drj- and then complete the process : if there is 

 sufficient time available the latter is the better way, but each 

 time a fresh brushful of cement is taken, it should be pre- 

 ceded by a dip in the solvent. The cement can then be 

 deposited with cleanness and regularity. 



Lectures. — We have been apjdied to by a small Natural 

 History Society for a lecturer or demonstrator, who would give 

 an evening of- practic.ll ex])lanation of the principles and working 

 of the microscope and its appurtenances. We should be glad to 

 know of one who would like to make himself useful in this way 

 and to put him in communication with our correspondent. A 

 fee would be paid if necessary. 



XoTES AND Qi-ERIES.— -I//-. A. H abb'j rcl . — The "chalk 

 which yon have been cleaning for Foraminifera is probably a 

 manufactured article and consequently would be useless. Lime- 

 stone from a cliff would be sure to yield the material you 

 required. If vou have not an opportunity of collecting this 

 yourself, and will let me know, I shall be happy to send you a 

 small quantity that would give you good results. 



Communications and enquiries on llicroscopical matters are 

 cordially invited, and should be addressed to M. L CROSS, 

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

 ♦ 



NOTES ON COMETS AND METEORS. 



By W. F. Denntng, f.b.a.s. 

 Comet 1898 Til. (CoDDnfGToy). — This object, like the comets of 

 Barnard (1892 Y.) and Chase (1898 Till.), was discovered by 

 photography, and it remained visible for a considerable time. The 

 observations, which number more than 400 in the aggregate, have 

 been rigorously discussed by Mr. C. J. Merfield, of Sydney, and he 

 gives definitive eleir.cnts in Ast. Xach.. 3684-5. The oomet passed 

 its perihelion on 1898, September 14th, 0442, and its orbit appeai-s to 

 deviate very slightly from that of a parabola. 



The Discovert op Comets. — As far as is known there is at 

 present nothing observable in the way of cometary objects. The 

 small comet discovered by Giacobini in December last has now 

 travelled beyond the range of our best telescopes, and the expected 

 periodical comet of Brorsen has not yet be«n re-detected. But we 

 shall probably not have long to wait for the discovery of new objects 

 in this field, for March and .April have been usually more productive 

 than the winter months in furnishing them. Xo doubt many comets 

 elude observation altogether, as the search for them is subject to 

 many irregularities, and is very far from being exhaustive. The fact 

 thata proportion of the known comets were found at times when they 

 were long past perihelion, aad were on the point of disappearance 

 through increasing distance, warrants the inference that every year 

 there are several small comets which visit our parts of space, and 

 leave it without being sighted by those astronomers who make it their 

 duty to search for these bodies. Some of the observers who have 

 previously occupied themselves in this work have done exceedingly 

 well, and established highly creditable records, but many additional 

 hands are required to complete the thorough exploration of the sky 

 month by month. 



FiBEBAit OF XovEMBEE 27th, 1900 — This object was seen at 

 lib. 10m. by Prof. A. S. llerschcl at Slough, Mr. H. Parsons at 

 Leicester, and Mr. J. T. L'herrymanat Plymouth. At the latter place 

 the meteor appeared to be very binlliant and large, falling in a 

 perpendicular direction from the Polar star. At Leicester the 

 observer was startled by the passage of " a liquid mass of fire which 

 illuminated the sty. and fell slowly in a dignified sweep towards the 

 south-west by south. ' Several frasments broke away from the central 

 mass during its flight. The radiant point of the meteor appears to 

 have been at about 47° + 45". and its height 57 to 17 miles over the 

 region of llfracombe. Its visible path extended over 40 miles, and its 

 velocitv was about 18 miles per second. Prof. Herachel has also 

 investigated the real path of this interesting object, and places the 

 radiant at 50^ + 45i°. He finds the heights 50 to 15 miles, the 

 length of path 35 miles, and velocity 16i miles per second. The 

 radiant between a. nnd /J Persei is that of a well-known shower of 

 slow meteors at the close of X'ovember and beginning of December, 

 and we arc- fortunate t<i have secured such a briUiant example of them. 

 FiEBBAXL OF Februaet 13th. 1901. — At lOh. 41m. Prof. Herschel 

 at Slough observed a fine meteor, equal to Tenus, traversing a short 

 course in Aries fi-om 30° + 17= to 25> + 12h^. It fell low in the west, 

 and was intercepted by the house roofs which formed the sensible 

 horizon. The meteor imparted a strong white glare to the sky for a 

 distance of about 10= around it, and it moved with moderite speed. 

 The same object was seen at Clifton passing down the skyto the right 

 of the Pleiades, from about 44° + 35° to 24= + 26°. "it was very 

 brilliant, but after a flight enduring two seconds, it passed behind 

 houses near the W. by X'. horizon. The probable radiant of the 

 meteor was at 72' + 41=. near 1 Auriga?, and this is really the focus 

 of a well-known shower between about February 5th and 15th. Its 

 height was from 56 io 26 miles, and path about 36 miles over 

 Pembrokeshirj". The..e results are only approximate, and it woiUd be 

 useful to hear of other observations. 



FlEEBALl, OF Febbuaet 27Tn. 1901. — Mr. Alex. Spark, of. 

 Aberdeen, reports an unusually brilliant meteor, at 8h. 4.Tm.. travelling 

 iu a X.W. direction. The colour of the head was bluish white, and 

 it left a trail of reddish sparks. The fireball was also seen by an observer 

 at X"ew Deer. Aberdeen, at 8h. 53m., passing through Ursa Major, 

 between tlie stars € and !;, and directed from between and 92 Leonis. 

 It remained in sight 10 seconds. At Lerwick, in the Shetland Isles, 

 Mr. A. Cadenhead noted the meteor at 8h. 51m., and describes it as 



