Januaky, 190S.] 



KNOWLEDGE. 



21 



amount of interest that has been taken in metallurgical work, 

 a department in microscopy which is destined to exert a great 

 influence on metal work generally. The capabilities of the 

 microscope in this direction are not yet completely realised, and 

 we may look for further development in the near future. 



Among other items the two-speed fine adjustments have 

 created interest and three or four new models of microscopes 

 have been introduced. 



There is, undoubtedly, better understanding of the proper uses 

 and applications of the microscope, the substage condenser and 

 the objectives, and when once the ])rinciples of critical illumina- 

 tion are thoroughly grasjjed and practised microscopical work 

 generally will be uniform and far more trustworthy. It is but 

 a few years since some degree of eminence was accorded to a 

 well-known histologist for his investigations of certain 

 structure, and the supjiosed discovery of new facts and detail 

 which he demonstrated by photo-micrographs; yet it was 

 evident to those who worked "critically" that the new features 

 were almost entirely introduced by errors of illumination, and 

 this was proved when his methods of working became known. 

 Yet his dicta were accepted, reviewed and praised. 



In another case a microscopist, who worked according to 

 modern knowledge and practice, was being examined for a 

 degree, and, amongst other things, was called upon to " spot" a 

 subject which he had for several years studied and made 

 especially his own. Owing to the indifferent method adopted 

 by the examiner in illuminating and arranging the microscope, 

 he failed to identify the specimen until he had bethought 

 himself to re-arrange the setting up. I make special reference 

 to this subject because it appears to me to be a real desideratum 

 that microscopists shall work in the most precise manner that is 

 known : it is only as work is accurately done that it becomes of 

 real value. 



In the conduct of a column such as this, the variety of 

 information given and the general usefulness could be greatly 

 increased by the co-operation of readers. 



As mentioned in the December number, arrangements have 

 been made for articles by several specialists to appear, but 

 beyond this there are many readers who have made some 

 special department the subject of study for a long period, and 

 are in a position to give directions and advice which would be 

 invaluable to other microscopists. Others have had constructed 

 to their S|)ecial ideas pieces of apparatus wliich they have found 

 serviceable, or have distinctive methods of working which are 

 not generally practised by others. 



Among instances of these might be mentioned the method of 

 showing a living fly in the act of feeding which was devised by 

 the late Mr. Macer, and the beautiful colour arrangements 

 which Mr. Rheinberg has brought to such jjerfection. 



Communications are cordially invited, and aided by the 

 consultants who have kindly placed their services at the disposal 

 of readers of this column, I shall be happy at all times to give 

 every assistance and advice in my power to those who may wish 

 to avail themselves of it. 



Wanted a MiCROSCoi-li Taisle. — In the November number 

 suggestions were invited for a comprehensive microscope table, 

 wliich could be closed and left with work in hand, ready to be 

 proceeded with at some convenient subsequent time. 



I have received several suggestions, but undoubtedly the best 

 of all is the table which Mr.^T. H. Russell, of Edgbaston, had 

 built to his own ideas some years ago. An illustration of it is 

 appended. 



The following are its dimensions : Height, 2 ft. ft in. ; 

 measurement of top, 15i in. by 24 in. 



It also has a hinged flap, suspended from the back of the 

 tahle, 11 in. wide, on whicli mounting, etc., is done. 



The table is Htted with a drawer which is divided into some 

 eighteen compaitments, similar to the plan shown. In this are 

 contained dissecting instruments, cover glasses, glass slips, spirit 

 lamp, saucers, and general accessories. 



The loose wooden lid or cover, about i^ in. deep, fits over 

 the top of the table, and is provided with two locks, one at each 

 end, by means of which it can be fixed to tbe top of the table, 

 and tlius covers any work which may be in progress. Two 

 strong handles are fixed to the sides of the table for lifting. 



This table has one great merit — sim])licity — and would un- 

 doubtedly cover the requirements of four-fifths of the working 

 microscopists. It will be readily seen that it could bo made, if 



desired, at a very moderate expense, and modifications to suit 

 individual tastes and requirements could be readily introduced. 



^: ~" ^.-/7 



c [ 



c^ 



)^ 



U 



Pe I 



A. Moveable cover; BB, Locks ; C C, Handles; D, Flap. 



For those who cared to do it, it would, of course, be possible to 

 raise the lid by means of a pulley wheel attached to the ceiling 

 and a weighted cord ; and 

 if it were desired to leave 

 the microscope in position, 

 the shape of the cover could 

 be made so that it would 

 go down over tbe micro- 

 scope and lamp in situ. 



To minimise vibration, 

 the feet of the table could 

 be inserted in sockets 

 padded with india-rubber. 



Our correspondent has 

 in addition a cupboard in his 





Plan of Drawer, showing divisions. 



hall where various articles such as a supply of water, bottles, 

 and receptacle for waste water, etc., are always at hand. 



Practical Schk.me. — In continuation of the attempt made 

 last year to foster practical work, material will from time to 

 time be offered for distribution as hitherto. Through the 

 courtesy of a reader I am able to offer some very interesting 

 Spongilla and sponge spicules. A small supply will be sent 

 to applicants on receipt of a stamped addressed envelope 

 accompanied by the coupon to be found in the advertisement 

 pages of this issue. 



Mr. R. G. Mason, of Clapham, calls attention to his series of 

 unmounted specimens, and has given me an opportunity of 

 seeing the Limestone and Coal sections that he is advertising. 

 The former would be found very useful to those who require 

 practice in mounting; the prepared specimens are cleanly 

 mounted and show interesting structure. 



NOTES AND QUERIES. 



C. M. — You are quite right, the deep curve of the crossed 

 lens of an Abbe illuminator should be mounted downwards, 

 that is, in the direction of the mirror of the microscope. The 

 focus you mention is unusually long for an Abbe illuminator of 

 correct form. 



//■. T. — I am afraid I cannot add to previous information. 

 You ought easily to get a good black background under the 

 circumstance you name, it is entirely a question of manipulation. 

 Presumably you use the plane mirror. While you failed with 

 the Abbe illuminator alone, there was a chance of something 

 being wrong, but seeing that you do not succeed with a spot 

 lens either, it seems certain that some little detail in your 

 working is not attended to. 



ir. D. /j.— The difficulty you mention of obtaining the same 

 polarisation colour efliects by artificial as with daylight is always 

 a somewhat difficult matter. The only suggestion I can offer is 

 that you set up a light filter consisting of a trough containing a 

 blue medium of acetate of copper or animoniacal solution of 

 sulphate of copper, and then by varying the strength to find 

 the tint which will give you the desired result. Perhaps some 

 of our readers who do petrological work may know of some 

 other and better method. 



