January, 1002.] 



KNOWLEDGE 



21 



tho skill and judgment of the operator, and is largely a 

 matter of practice. The residuum in the jar must bo 

 washed out into a basin for further treatment, and 

 tlio operation repeated with more sand and water until 

 the whole of the gathering has been treated. The time 

 allowed for subsidence will vai-y with the fineness of 

 tho sand, so that in the case of the finest siftings, nearly 

 a minute may be required. The actual time can only 

 be determined by watching the falling material in a 

 strong light. 



In tho case of very fine sand the tension of the surface 

 film of water is so great that the sand giains float almost 

 as readily as the Foraminifcra. This difficulty may be 

 overcome by shaking up the contents of the jar, covering 

 up the top with one's hand while so doing. 

 {To be continued.) 

 (See Note headed "Practical" hehir.) 



Conducted by M. I.Cro§§ 



Retkosi'ECTIve. — The year Ulnl did not witness any startling 

 development in connection with the microscope, but it was one 

 in which a steady progress was shown in nearly every department. 



It witnessed the introduction of several new stands principally 

 for students' use, two-speed fine adjustment devices, the increase 

 in number and variety, and, above all, in the aplanatism of sub- 

 stage condensers and the substitution of actual working data for 

 appro.ximation in the case of tube lengths and cones of 

 illumination. 



In processes there were many new formula recorded, and 

 judging from the number of articles which appeared on the 

 subject, the science of micro-metallurgy is rapitUy advancing. 

 In the domain of preventive medicine, the best points of tlie 

 microscope are becoming more fully appreciated and worked to 

 greater advantage, and results are becoming increasingly 

 reliable. 



In literature the fresh edition of Carpenter on the Microscope 

 was a feature of importance, and the paper read by Mr. J. W. 

 Gordon before the Royal Microscopical Society in controversion 

 of the Abbe theory of microscopic vision is still fresh in the 

 memory. 



On the whole, microscopists can congratulate themselves on 

 the work done in the past year. 



Cooi>Ki:.\Tiox. — So much of the progress in microscopy in 

 recent years has been attributable to the work of a few 

 individuals that it has almost been lost sight of that the rank 

 and file can and should do their share. 



It is eminently desirable that a column of this kind should 

 be made the medium for conveying the thought, research and 

 observation of microscopists generally. The subject is so 

 many-sided that it is impossible for any one individual to 

 present it in its various aspects, and it is for those who catch 

 glimpses and side lights that others do not notice, to add 

 interest and increase knowledge by communicating their 

 observations. There is scarcely a microscopist possessing 

 enthusiasm, or who works ihoughtfully, who has not found 

 some little device of his own designing useful to him, or some 

 process which has enabled him to produce more ►atisfactory 

 results than by stereotyped means. Readers of these notes 

 would always appreciate a short description of such methods, 

 and by the communication of such ideas increased perfection 

 would be attained. 



Pit.vcTir Ai.. — If microscopists generally can but be induced to 

 become practical workers, that is, to prepare and mount their 

 own slides, an increased interest and wider knowledge would be 



the result. Tho difficulty invariably is that suitable material 

 cannot be procured ; as an instance of this, I may mention that 

 in the April number I offered to send a correspondent a small 

 supply of Polcystina, and later mentioned that a supply was at 

 the disposal of others. The applications that I received for 

 samples indicated that there are numerous readers willing and 

 anxious to mount their own specimens. Yet another in.stance ; I 

 have a letter from a correspondent, from which the following is 

 an extract : — 



" I hoped during the past summer to have been able to collect 

 some specimens of Mycctozoa, but have not found one. What 

 I want to suggest is that those collectors of such fungi who live 

 in districts where they are found abundantly, should distribute 

 their findings to those who are not so fortunate, by way of 

 e.vehange, or for my own ))art I would willingly reimburse any 

 expense in sending, as I should much value even a small 

 collection. There must be many who have neither time nor 

 opportunity of collecting who would gladly avail themselves of 

 such an arrangement." 



With these facts in view, it is proposed during the next few 

 months, as far as possible, to offer material for readers to mount 

 themselves and to give lucid instructions for doing the work. 



In this number Jlr. A. Earland contributes the first portion 

 of an article on " Collecting and Preparing Foraminifera,'' and 

 with the February number we shall hope to offer gratis to 

 readers a supply of different kinds of material so that each may 

 for himself practise the methods set forth. 



I shall be very glad to hear from readers who are willing to 

 help in th^s scheme, and who may be able to contribute notes 

 from their own store of experience, or material for distribution. 



I am glad also to be able to say that the experimental offer 

 made in the last number to send a substage condenser for 

 examination has received appreciation, and that manufacturers 

 have arranged to co-operate so that the offer may be renewed on 

 future occasions when other apparatus is reviewed. 



NOTES AND QUERIES. 



Her. A. II. M. — It is certainly advisable to use colour sensitive 

 plates for photo-micrography. I cannot recommend any special 

 brand, but you would find Cadet Spectrum, Ilford Chromatic or 

 Edward's Isochromatic quite satisfactory. Colour filters are also 

 of very great importance, but you could readily learn their 

 value from any work on photo-micrography. The photograph 

 you send is a very good one of starch granules, especially con- 

 sidering it is the first attempt. You will find it necessary 

 with a view to getting true images to use a larger aperture 

 than you have in this instance, your condenser was evidently 

 very much stopped down. 



E. A. — No ordinarj" gas lamp is really satisfactory for critical 

 micro work : still a very useful and simple pattern is employed in 

 laboratories, and can be obtained for a nominal sum. It consists 

 essentially of an u])right rod attached to a round base, upon this 

 rod a horizontal supporting bracket slides vertically and is fixed 

 by a clamp screw. The horizontal arm carries an Argand 

 burner and a chimney. I believe this can be obtained from Mr. 

 A. H. Beard, of Lothian Street, Edinburgh, with a blue chimney. 

 I know of no suitable acetylene lamp. Alternatively, the 

 Welsbach mantle and burner can be used, of which you will 

 obtain particulars from the Microscopical Notes in the May, 190 1, 

 number of IvNoWLEncK. 



//. J. II. — The only maker I can trace who supplies an 

 objective adjustable from 2" — 4" is W. Wray, of Laurel House, 

 Highgate. I think you would get what you required from him. 



<T. W. B. — From the description you give you could not do 

 better than have one of the Cathcart's pattern Microtomes ; the 

 diificulty you experience with the small hand section cutter 

 would be satisfactorily overcome with this. 



Reiiili'i- '/" Kiitjirlcdi/e." — I am sorry to say I cannot identify 

 the specimen you send, nor can I trace in any book the name of 

 " Paludicella." I am not aware of any book being published 

 dealing with Growths in Water-pipes. 



Acarina. — The state of things that you describe in connection 

 with your furniture is very disagreeable, but no serious conse- 

 quence is to be apprehended so far as the wood work is 

 concerned, from the acarus you have sent. This is the Book 

 or Museum Mite — Che;/leliix eruil/tas. I should be disposed to 

 think that these live and multiply in the upholstering of the 

 furniture. Shreds of sea-weed have been known to be substi- 



