Decembeb, 1902.] 



KNOWLEDGE 



285 



Conducted by M. ICrp^^ 



Progkamme for 1903. — It is intended in future to devote a 

 larger amount of space to Microscopy than hitherto, and by the 

 cooperation of specialists to publish articles treating on 

 different departments of both the popular and scientific sides. 

 Among those who have promised to contribute are the 

 following :— Mr. Rousselet, " How to Collect Rotifers," and 

 "How to examine Pond Life under the Microscope"; Mr. 

 C. U. Soar, " The Collection, Examination and Preservation of 

 Water Elites ' : Mr. Earland, "Coccoliths and Coccoopheres " ; 

 Mr. AVeschr, " The Mouth Parts of the Tset.se Fly in comparison 

 with those of the Gnat, (iad Fly, etc.," and notes on entomo- 

 los;ical subjects ; Mr. F. Noad < 'lark, " The Photography of 

 Dpaque Objects" ; Mr. Sanger Shepherd, "' Photo-Micrography 

 in Natural Colours '' ; and other similar articles will appear. 



It is ho|)ed that these new arrangements will greatly increa.se 

 the value of the microscopical notes, and maintain the interest 

 which has so far been evinced. 



As occasion offers, specimens will be offered for distribation 

 as in the past year, and the assistance of readers who may be 

 able to spare interesting material for the purpose will greatly 

 increase the usefulness of this section. It is hoped that some 

 Spongilla, spicules of sponge, etc., will be available for the 

 January number. 



Po.ND-LiKE Coi.LEcriNC. IX DECEMBER.— Severe weather in 

 this country does not, as a rule, set in in December, and the 

 lakes and ponds are not usually frozen over in the early part of 

 the month. The winter fauna has now become more pronounced, 

 but includes quite a number of Infusorians, Rotifers aud 

 Crustaceans. The following species of Rotifers have been 

 collected in December in lakes and canals in and round London, 

 some of them in great abundance : Anurira aouleata and 

 cm'hleariii, Asplanihna brii/lifirflti and lyriudoiild, lirachimius 

 angulai-in, Diaxchha .temiajierla, Euchlanis dejiexa. Melicerta 

 riiigens, Oeci.iti's cri/ntiillliiun, Limnias rcrat>jjjlii/lli, Floacularia 

 cornuta, Si/iiclueta jjectinalJ and fremuhi. Conochilu't unicjrnis, 

 Rotifer vulgaris and marriirus, Pohjarlhra platyptera, Sullmlca 

 scajihii, Triarthra lungiieta. Of Crustaceans, Diaplomas 

 i-(/.v?o/- and various Ci/clups and their larvae are abundant, whilst 

 Waterfleas die down. A minute red flagellate Infusorian often 

 seems to form the chief food-material of the above lake fauna. 



A few of the principal collecting grounds for Pond-life in and 

 near London may be mentioned. The nearest ami most con- 

 venient available piece of water is the Grand Junction and 

 Regent's Canal, which runs from east to west, on the northern 

 side of London, from Victoria Park to Hanwell, and is readily 

 approachable wherever access can be gained to the towing path. 

 Then all the great parks have a lake, such as Victoria Park, 

 Regent's Park, Hyde Park, Richmond Park, Wimbledon 

 Common, etc., which all afford good collecting grounds. Smaller 

 ponds are found in abundance in fields and commons in and 

 beyond suburban London, and I need only mention a few such 

 places : Epping Forest, Higham Park, Hauley Wood, Totteridge, 

 Hampstead Heath, Ealing Common, Hampton Court, Patney 

 Common. 



MiCRoscoTE Construction. — The fact that the majority of 

 the British makers of microscopes have to a greater or less 

 extent conformed to an orthodox pattern of microscope stand, 

 would lead one to imagine that for the time being, at any rate, 

 finality had been arrived at, and that the best possible in 

 microscope stands was at the disposal of microscopists. The 

 Continental people, with very slight exceptions, also adhere to 

 a model which is wonderfully uniform, so far as its advantages 

 are concerned, in the different makes. 



The " Xelson " model microscope, supplied by C. Baker, was 

 practically the prototype of all the later tripod foot instruments, 

 but is the tripod foot as at present made the best possible for 

 convenient working '/ What is the real advantage of having 

 straight legs to the front instead of those which may be slightly 

 curved, so that access to the subsfcige and its apparatus (especially 

 in microscopes of small size) may be as conveniently attained as 

 in those microsojies which are built on a horseshoe base 'i* 



Microscopists are at last realizing the advantages derivable 

 from a tripod foot, but it is very desirable that disadvajitages 

 associated with this pattern should be removed. There is still 

 room for a fine adjustment which shall be carried by the rack- 

 work instead of itself carrying the rack work portion of the 

 instrument. Swift's " Climax," which he still fits to his 

 " Challenge " aud " Paragon " stands, is one of the best devices 

 of this kind, but the laboratory worker wants a fine adjustment 

 milled head in the usually accepted place at the back of the 

 limb. 



The mechanical stage certainly needs a greater range of 

 movement, and the milled heads should be below the level of 

 its up])er surface. The Continentil makers get over this 

 difficulty bysup))lying controlling heads of very small diameter, 

 which of necessity cannot impart that fine movement which is 

 to be found in the British microscopes. Mr. Nelson many 

 yeiirs ago devised a mechanical stage having vertical rack-work 

 movement only, and in order to bring the controlling milled head 

 below the level of its surface, fitted the rack itself beneath the 

 main plate of the stage. 



The difficulty that always arises in giving a long movement 

 to a stage is that of the upper lens of the conden.ser fouling the 

 plates!, but this can be obviated, especially with the smaller 

 mounts carrying the achromatic condensers which are so largely 

 coming into vogue. 



Then a greater range is required in the body length. I have 

 had specimens sent to me for examination by readers which 

 have been covered with a glass which could only justly be 

 described as attenuated window pane. The wonder is that any 

 self-respecting microscopist could ever spoil his objects by 

 protecting them with such covers. Some 1 have been unable 

 to examine with a high power at all, while others for critical 

 examination have necessitated an exceedingly short tube-length, 

 sometimes four inches only. This cannot be arranged on the 

 average present day model of microscope. 



Then — for amateur purposes especially — it is often felt that 

 there should be a greater interval between the upper surface of 

 the stage and the lower part of the limb of the microscope. 

 The modern microscope is built very closely, and the earlier 

 type, such as the Swift " Challenge " mentioned above, is 

 altogether superior in the comfort it affords in this respect. 



A handle by which to lift the microscope has been provided 

 in Zeiss' new photographic stand ; this is a convenience which 

 would be much appreciated in other microscopes. 



Such matters as these which have been referred to can be 

 more easily incorporated in a microscope of large size than in 

 the popular medium-sized models, but it is to be hoped that the 

 inventive faculty may not become dormant in microscopical 

 matters — there is room for improvement yet. 



It is impossible to deny the tribute that is duo to Messrs. 

 Powell & Lealand for the prevision which caused them to 

 incorporate many of these features in their large model stand. 

 Jly own feeling has never been in favour of a coarse adjust- 

 ment on a bar fitting ; it certainly does not meet the needs of 

 every class of worker in a way th;it the more recently designed 

 stands have done. Could not the better points of the Powell 

 stmd be incorporated in other instruments by the exercise of 

 ingenuity ? 



Micro. Pro.iection. — A very large number of those people 

 who pos-sess microscopes also have a magic lantern, and a con- 

 siderable amount of jileasure can be imparted by the ])rojection 

 of micro, specimens upon the screen. Several neat attachments 

 are made to screw into the magic lantern in place of the 

 ordinary lens, and, with suitable condensers and the use of the 

 ordinary micro, objectives, fair results can be secured. It is 

 essential that limelight be used as the illuminant, or, preferably, 

 an arc lamp; anything less than either of these produces dismal 

 results. 



