December, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



309 



W., on October 20, the President, Dr. E. J. Spitta, 

 F.R.A.S., in the chair, Mr. James Burton read a paper, 

 " On an Easy Method of Staining and Mounting 

 Micro-AlgEe and Fungi." The method described may 

 be briefly summarised as follows : — Fix the fungus by 

 one or more drops of 90 per cent, alcohol; follow with 

 25 per cent, alcohol; wash out with distilled water; add 

 a drop of glycerine stained with Hoffman's blue, and 

 cover. The fungus absorbs the stain from the 

 glycerine, which acts also as a preservative medium. 



Mr. F. P. Smith continued his revision of the classi- 

 fication of the spiders of the sub-family Erigoninae, 

 dealing with those species which he included in the 

 Walckenaeria group. A complete bibliography of the 

 group will appear in due course in the Club's journal. 



Mr. .Smith also described a new British spider from 

 Great Yarmouth, under the name Anglia hancockii. It 

 is one of the largest known forms of its sub-family, the 

 Erigoninae, and appears to be of a very early type. 



There was a crowded meeting of members, who 

 listened with regret to the announcement of the death 

 of their veteran Vice-President, Mr. J. G. Waller, who 

 had died on the previous day at the great age of 92. 

 Mr. Waller, who was also well known as an artist and 

 archaologist, joined the Quekett Club in 1868, and had 

 served for a great number of yeais on the Committee. 

 He was elected President of the Club in 1896 and again 

 in 1897, ^nd served as a Vice-President from 189S until 

 his death. 



Notes and Queries. 



Capt. H. D. Foulkes, Fort Purhrooh. — Your question raise.s 

 an interesting and practical point. The resolving power, that 

 is, the ability to separate a maximum number of lines to the 

 inch, is directly dependent upon the numerical aperture of the 

 objective. Therefore a ,1 inch of N.A. 1-5 will tlieoretically 

 have the same powers of resolution as a ,\, inch of the same 

 aperture. But to resolve a number of lines and to make them 

 evident to the eye are two different things. The average 

 normal eye is generally stated to be able to distinguish 200 

 lines to the inch at the normal visual distance of 10 inches. 

 Therefore the image given by either ol:>jective must be magni- 

 fied sufficiently by the eye-piece to make such lines distin- 

 guishable by the eye. Now, in theory apochromatic objectives 

 will bear any amount of eye-piecing, but this is not so in prac- 

 tice, even apart from the loss of light, and the higher powers 

 bear high eye-piecing less satisfactorily than the low powers. 

 These limitations are still more evident with achromatic objec- 

 tives. So that if the maximum resolution be imperatively re- 

 quired a ,'. inch of N.A. 1-5 would in practice be less satisfactory 

 than a higher power of the same aperture because of the high 

 eye-piecing required to make the lines visible. But if such 

 maximum resolution be not requisite, in other words if the 

 object does not need such extreme resolution, then there are 

 several advantages attendant upon the use of the lower-powered 

 objective of the same aperture, t^irstly, the working distance 

 is greater; secondly, the field of view is larger; thirdly, the 

 loss of light of the two objectives is proportional to the square 

 of the magnification ; and fourthly, though the amount of light 

 dependent on the aperture varies as the square of the N.A. 

 (which of course in any pair of objectives increases in a much 

 smaller ratio than the magnification) in the two objectives 

 under discussion the N.A. is identical. Tlierefore. if the work 

 is of such a nature that moderate magnification only is re- 

 quired the lower-powered objective is preferable. With a pair 

 of still higher powers of equal aperture the lower power would 

 be preferable under almost all circumstances. Let us take for 

 instance a jij inch achromatic of N.A. vz^ and a y", inch of 

 the same aperture, or an apochromatic 5 inch of N.A. i'4 and 

 a ^, incli of the same aperture. In the first case a quite 

 moderate eyepiece, which the objective can well stand, will 

 show all that a ^. of N.A. 1-25 can resolve and the drawbacks 

 incidental to using a ^^ inch of higher magnification, but of 



the same aperture will bring with them no compensating 

 advantage. With the pair of apochromatics of N.A. 1-4 the 

 I inch will require rather higher eye-piecing to make the 

 maximum amount of structure evident, but still it will not be 

 more than an apochromatic can well stand, and so it again is 

 preferable to the ji.lh. 



./. T.Orme, Kor/c— For the chemical tests for mechanical 

 wood pulp and esparto grass (as aids to microscopic exami- 

 nation only) I must refer you to my series of articles in 

 " Knowledge " on the "Fibrous Constituents of Paper " in 

 the issues of February, March, April, and May of this year, 

 pages 42, 68, 92, and 114. There are no chemical tests in 

 bulk, unless the somewhat untrustworthy use of aniline sul- 

 phate as a test for mechanical wood pulp may be looked upon 

 as such. Cross and Bevan's book is the best text-book on 

 papermaking, and deals with such chemical analyses as are 

 practicable for paper. Griihn and Little's book is more a 

 manual of chemistry specially written for papermakers. A 

 very good little book in certain respects is Hertzberg's 

 " Paper Testing," tianslated by Dr. Norman Evans, and pub- 

 lished in 1S92 by W. J. Stonhill, at the offices of the Paper 

 Trade Revic-cV. This is the nearest of the German books to 

 what you require. I am afraid I cannot give you any infor- 

 mation on the subject of "smalt," other than you appear to 

 have already, and I am sorry that the many claims upon my 

 time will not permit of my making an analysis for you of the 

 sample you send. 



Major E. F. BccJur, Chi-ltc]iha>ii. — You do not give me the 

 focal length of your bullseye, so it is not quite easy to answer 

 your question definitely. The most obvious suggestion is that 

 the 2 inch objective takes in a larger field than the sub-stage 

 condenser could illuminate, until in altering both condensers 

 you adjusted the latter so that the rays crossed and thus 

 illuminated the wliole field. If you were using one of the 

 ordinary Abbe sub-stage condensers and not one of the new 

 macro-illuminators, this is probably the correct explanation. 

 Of course, if your Ught were correctly focussed upon the object 

 you would get a disc of light smaller than the objective with 

 the I inch also, but the spherical aberrations of the bullseye 

 you had interposed between the light and the sub-stage con- 

 denser would prevent such accurate focussing, and you would 

 thus get a disc of light large enough to illuminate the whole 

 field taken in by the latter objective. With regard to investi- 

 gations into the nervous system of insects, a certain amount can 

 be done by careful dissecting, especially in gaining a true im- 

 pression as to the relations of various parts. This will, of 

 course, need to be done under a dissecting microscope and 

 probably under water, the insect being pinned down to wax 

 run into the bottom of the dissecting dish or to a piece of cork 

 weighted with lead and placed in the dish. I do not think it will 

 be practicable to attempt to stain the nerves and their ganglia 

 in situ by any differential stain which will stain the nerves only, 

 whilst the other parts and the chitinous exo-skeleton are left 

 transparent. Your method will therefore be to proceed by 

 means of serial sections, both transverse and longitudinal, and 

 this will need careful preparation of the object beforehand, and 

 a certain amount of experiment before you decide on the best 

 fixing and other reagents and stains. For fairly thick sections 

 the celloidin method will do, and the sections can then be cut 

 with any good microtome. But for really first-rate sections 

 the object must be prepared for infiltration with paraffin (not 

 embedding merely), and be cut on a good rocking microtome 

 such as the well-known instrument made by the Cambridge 

 Scientific Instrument Company. Have you had any experi- 

 ence of infiltration methods ? If so, your task will be greatly 

 lightened. You will probably have to stain the sections upon 

 the slide by some differential nerve stain. Eau de Javelle 

 would probably be a good method of making the chitin trans- 

 parent, as it is stated to have no effect upon such delicate 

 structures as nerve endings and to render the chitin permeable 

 to staining Huids, but my experience has betn that it requires 

 to be used with great care. The sohition should be diluted to 

 4 or 6 times its volume of water, and the object left in this for 

 24 hours, or much moie, accordirg to size. You might use 

 this reagent before dissecting. If you then wish to go on to 

 make serial sections, I will try to explain how to set about it. 



[Communieiitions tiini Eiicjiiiries on Microscopical maltirs should he 

 iiddrcsscd to F. i:hiiiington Scales, ^'Jersey," St. Barnabas Hoad, 

 Cambridge.'] 



