April, 1904] 



KXOWLl'DGl-: lS: SClENTll'lC Xl-WS. 



75 



Modern Navigation, by W. H:ill. K.N. (Organised Scionce 

 Sories.i L'niversitv Tutorial I'ross. _ 



SeconJ Stage Botany, by J. M. Lowson. (Organiseci Science 

 Series. I Iniver^itv Tutorial Press. 



Entropv.bv lames Svvinbunu-. iConstable.l 



The .Modei Engineer Series.— X-rays, Simple Experiments n 

 Electricity, The Locomotive, Acetylene Oas. ( IVrcn al Marshall.) 



A School Geometry. Tarts 1. IV.. by H. S. Hall: IV. and 

 v.. F. H. Stevens. (Macmillan.) 



We have received from Messrs. Nalder Bros., ot \\ est- 

 minster, their catalogue of Electrical Testing and Scientific 

 Instrument!!. The catalogue is, in itself, an e.\trenuly in- 

 teresting summary of the investigations now binng carried on 

 in various departments of research, and special attention may 

 be directed to the photometric apparatus. 



Tin following hocks an- in pnpurtttUm at the Claraulon Press i - 

 Suess' •' Das Antlitz der Erde." authorised English transla- 

 tion, by Dr. Hertha Sollas. edited by Professor W. J. Sollas, 

 with preface by Professor Suess for the English translation. 

 Koval i-vo. ,, , 



"Index Kewensis Plantarum Ph,anerogamarum. Supple- 



mentum secundum. 4to. 



Goebels -'Organography of Plants," authorised English 

 translation, by I. Bayley Balfour, M..\., F.K.S. Vol. II. 

 Roval Svo. 



Mr. Henrv Frou.dc u-ill also publish shortly :— 



•• \ History of the Daubenv Laboratory," bylK. T. Gunther. 



Conducted by F. Shillington Scales, f.r.m.s. 



Royal Microscopical Society. 



February 17, Dr. Henry Woodward, Vice-President, in the 

 chair. An old microscope by Bate was exhibited, probably 

 made early in the last century. Mr. Stringer contributed a 

 paper on an attachment for reading the lines in a direct-vision 

 spectroscope, and Mr. E. M. Nelson a paper on the vertical 

 illuminator. The author said that, after lying in abeyance for 

 25 years, the vertical illuminator had lately come into notice 

 for the examination of opaque objects, and especially for the 

 microscopical examination of metals. He criticised the four 

 forms of this apparatus at present sold, namely, those known 

 as the ToUes, Beck, Powell, and Reichert forms, and said 

 that a vertical illuminator must not be an oblique illumina- 

 tor, but must be capable of illuminating the full aperture of 

 the objective with a parallel beam of light. It must not impair 

 the use of the objective for ordinary work, and must, there- 

 fore, not be a permanent attachment. The reflector must be 

 placed near the back lens, and there must be some method 

 for regulating the illumination. Mr. Nelson found that the 

 Powell form, which, like Beck's, consists of a nosepiece con- 

 taining a reflector, more nearly conformed to these conditions, 

 but the reflector should be made much larger and the hole in 

 the side of the nosepiece should be as large as the Society's 

 gauge. To obtain the best advantage with vertical illumination 

 oil-immersion ol>jectives should be used. The distance from 

 the source of light to the mirror and thence to the objective 

 should be equal to the distance from the eyepiece to the 

 objective. At the hole at the .side of the nosepiece there should 

 be a carrier for diaphragms of various sizes in preference to a 

 wheel of diaphragms or an iris. There should also be a strip 

 of metal with a slit in it which could be drawn across the hole 

 in the nosepiece, and the direction of the slit should be in a 

 line with the edge of the flame of the microscope l.uiip. 

 Another paper l)y Mr. Nelson, "On the Influence of the Anti- 

 point on the Microscopic Image Shown Graphically" was also 

 read. The author referred to a papt^r in tlic Journal for 1903 

 on "A Micrometric Correction for Minute Objects." wherein he 

 stated by way of illustration that, if one of the minute spinous 



hairs on a blowfly's tongue was exaiuiiied on a bright ground 

 and on a dark ground, a considerable difference in the sizes of 

 the two images was diseeniilile, aiul that the diflerence was 

 caused by anti-points. .\ talile was also given showing the 

 amount to be ailded to the niicronietric ineasureinent of the 

 image seen on the bright ground to bring it up to its true \ alue. 

 Mr. Gordon, who had originated the theory of the anti-point, 

 had made accurate drawings of the two images of the hair, 

 and the ratio of the breadths of the hair in the drawings was 

 as 45 to 05. Applying the corrections given in the table to 

 the measurement of the apparent size of the hair on a bright 

 ground, the actu.il size works out to 12 per cent. more. A 

 ditference in the apparent size of objects when viewed on a 

 bright or dark ground was recognised many years ago, but 

 never explained, but M r. Gordon's admirable anli- point theorem 

 has unlocked the riddle. Mr. Keith Lucas followed with a 

 paper "On a Microscope with (Geometric Slides," the principle 

 enunciated being .applied by the author of the paper to the 

 fine and coarse adjustments' and to the sub-stage of a micro- 

 scope, which was illustrated by lantern slides. 



The Qviekett Microscopical Club. 



The aniiu.il gem ral meeting was held on 1 i bruary 19 at 

 20. Hanover Sipiar.-, the President, George Massee, ICsq., 

 F.G.S., in the chair. .Xfter the usual business had been trans- 

 acted, a ballot was taken resulting in the election of Dr. 

 Edmund J. Spitta, L'.K.A.S., as President for the ensuing year. 

 Mr. Frank P. Smith was elected Editor in succession to Mr. 

 D. J. Scourfield, and Mr. Arthur Earland, Secretary. Dr. G. C. 

 Karop, who has held the secretaryship for over twenty years, 

 goes into well-earned retirement, carrying with him the grati- 

 tude and esteem of all the ineml)ers. The other ofticers werc^ 

 re-clectcd. 



The President delivered his annual address, dealing with 

 the commoner fungoid diseases of garden trees and plants. 

 These may be divided into two groups, according to whether 

 the mycelium of the fungus is situated in the woody tissues of 

 the plant ("perennial mycelium "), or whether only the season's 

 growth, the leaves and fruit .are affected. The first division, 

 of which the well-known " peach-curl " is an instance, is by 

 far the more serious of the two, it being practically impossible 

 to cure a plant which has become badly infected. In the 

 second division, the plant becomes automatically purified, for 

 a time, on the removal of the infected leaves, &c., either artifi- 

 cially or in the course of nature, and if suitable measures are 

 taken to prevent the germination of the spores in the following 

 season, the plant may be wholly cured. Fire is the best 

 destructive agent; the infected leaves should be burned. 

 Spraying is ineffectual, for the mischief is under the surface, 

 and spraying tends to spread the disease to fresh hosts by 

 washing the spores off the infected plants. 



The chief causes of fungoid disease in cultivated plants are 

 overcrowding and the use of chemical manures, which kill the 

 nitrifying bacteria of the soil and stimulate the plant to an 

 excessive and weakly growth. 



After the usual votes of thanks. Dr. Spitta was installed in 

 the Presidential Chair, and in returning thanks for his elec- 

 tion, referred t<i the analogy between the fungoid diseases of 

 plants and the zymotic diseases affecting man, especially 

 typhoid and diphtheria. 



It is an open secret among microscopists that the (.Hiekett 

 Club's position at 20, Hanover Square has lately been some- 

 what precarious, owing to the general rise in rents and the 

 keen demand for accommodation in the building of the Royal 

 Medical and Chirurgical Society. I am therefore glad to be 

 able to say definitely that the Committee has succeeded in 

 obtaining an extension of their tenancy in their old quarters, 

 with retention of all their present accommodation, though at .1 

 considerable increase of rent, which will, I trust, be justified 

 by a corresponding increase of membership. To the amateur 

 microscopist, especially the Londoner, the (Juekett Club, with 

 its very low subscription of los. per annum, without entrance 

 fee, offers many advantages. The announcement was made at 

 the annual meeting that a new catalogue of the Club's fine 

 library of about ijoo volumes was in course of publication, 

 and this should still further increase the popularity of the 

 Club. Applications for membership and inquiries relating to 

 the Club should be addressed to the Hon. Secretary, Mr. A. 

 Earland, 31, Denmark Street, Watford, Herts. 



