May, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



with magnifications of from 400 to 600 — a statement, 

 however, which surely needs some qualification, whatever 

 may be the incidental disadvantages due to high eye- 

 piecing. However, Mr. Gordon's method of getting over 

 the difficulty is by the interposition in the tube of the 

 microscope of a ground-glass screen on which the image 

 is received from the objective, so as to scatter the inci- 

 dent rays of light, the screen being made to oscillate in 

 order to prevent its grain from becoming visible, and so 

 impairing the details of the picture. This picture can 

 then be magnified again by means of a second microscope 

 in place of an ordinary eyepiece, with consequent greatly 

 increased magnification. It may not perhaps be super- 

 fluous to remind my readers that the mere magnification 

 of an object, or even the rendering visible of what could 

 not otherwise be seen to b^ existent, as under Siedentopf's 

 experiment, does not give any optical solution as to its 

 true shape and size. In fact, it has been mathematically 

 proved, and remains true, to quote Lord Rayleigh's own 

 words, " In the microscope there is nothing except lack 

 of light to hinder the visibility of an object however 

 small. But if its dimensions be much less than half a 

 wave-length, it can only be seen as a whole, and its parts 

 cannot be distinctly separated, although in cases near the 

 border-line some inference may possibly be founded upon 

 experience of what appearances are presented in various 

 cases. . . . What has been said about a luminous 

 point applies equally to a luminous line. If bright enough 

 it will be visible, however narrow ; but if the real width 

 be much less than the half wave-length, the apparent 

 width will be illusory." 



Royal Microscopica.1 Society. 



March 15th, at 20, Hanover Square, Mr. A. U. 

 Michael, F.L.S., in the chair. Mr. J. E. Stead delivered 

 the second part of his lecture on micro-metallurgy, en- 

 titled " A review of the work done by metallographers," 

 illustrated by lantern slides supplied by prominent autho- 

 rities in several countries. Over 120 slides were shown 

 on the screen by means of the epidiascope, and were 

 accompanied by explanations and comments by the lec- 

 turer. The series commenced with the earliest work of 

 Dr. Sorby, followed by illustrations of the microscopic 

 characters of iron and steel, silver, lead, copper, tin, and 

 antimony. Illustrations were also shown of the changes 

 produced in metals by strains, a diagram of the apparatus 

 by which rapid reversals of strains were effected being 

 exhibited in illustration of this portion of the subject. 

 The effect of continued heating of an alloy of copper and 

 tin in boiling mercury and also that produced by immer- 

 sion in liquid air were demonstrated. Slides were also 

 shown to illustrate " surface flow " in antimony, and the 

 microscopic structure of the new silver standard. The 

 following were elected as Honorary Fellows of the 

 Society : Prof. Wm. Gilson Farlow, Prof. Herbert S. 

 Jennings, Prof. Edmund B. Wilson, and Prof. R. W. 

 Wood. 



Notes and Queries. 



Bausch and Lamb's New Catalogue. 



Messrs. A. E. Staley and Co., of 19, Thavies Inn, Holborn 

 Circus, E.C., have sent me the new illustrated catalogue and 

 revised price list of the Bausch and Lamb Optical Company, 

 of Rochester, New York. The illustrations, most beautifully 

 reproduced, make the catalogue quite a work of art. I 

 understand that it will be sent to any applicant on receipt of 

 three stamps to cover postage. 



Miss Frances EHiotl (Staines). — Crystals of lead nitrate would 

 be best shown by polarized light. Asbestos can be shown by 

 reflected light with a low power ; geological slides should 

 generally be thin enough to be shown by transmitted light. 

 A binocular would exhibit all these very well. I should strongly 

 recommend you to lose no time in beginning to make your own 

 slides — until you do this you can scarcely consider yours<!lf as 

 having started microscopical work, and you will not only find 

 the work most interesting, but will feel your interest deepened 

 in many ways. In the meantime dissect as much as you can, 

 so as to find out for yourself all you possibly can about 

 the object you are studying, aud read it up at the same time. 

 It is of the utmost importance to get an interest in some 

 definite line of study, and to endeavour to master the subject. 

 Pond life is most fascinating and teaches one many things 

 both in zoology and botany, and the present is a very good 

 time to begin. Ready prepared slides have, of course, an 

 undoubted educational interest, but they are not to be com- 

 pared in this respect with work done by oneself, especially if 

 it is the outcome of a definite aim. 



Alfred GoUisbnry (Mdxu\-Utozi'n, N.Z.). — It is quite common 

 to find parasites in insects such as you describe, but the in- 

 formation you give does not allow me to say more. The ova 

 also are in quite the usual place. If you want any further 

 information please send the slides themselves — they will be 

 duly returned if you wish it. 



A. H. Glaister (Darlingloii). — A 1-12 inch immersion of N.A. 

 f25, such as you possess, will readily resolve Amphlplciira 

 pelluciiia, and the Watson universal condenser is quite suitable, 

 but there is no advantage in using the latter in oil contact as 

 its aperture does not exceed I'o N..\. You say, however, that 

 your objective is corrected for the short tube, and it must 

 therefore be used with the short tube only. I think if you 

 carefully carry out the instructions I gave m " Knowledge " 

 for November last (page 279), you should has'e no difficulty in 

 resolving the diatom by means of oblique light, especially 

 if it is mounted in a medium of so high a refractive 

 index as realgar. The resolution by means of axial illumina- 

 tion is less easy ; it is best shown by carefully focussing the 

 edge of the lamp flame with the condenser and then slightly 

 racking the condenser up within its focus. Are you sure that 

 your objective is clean and free from oil on the front lens 

 behind as well as in front ? Human blood corpuscles may be 

 classified as follows : Red corpuscles, which appear yellow 

 when looked at singly, aud white corpuscles. The red cor- 

 puscles are circular discs, thicker at the sides than in the 

 centre, about 7'5 ^ wide and i'6 ij. thick (/i = "ooi millimetre) 

 and without nuclei. The white corpuscles are much less 

 numerous (about i in 500). They are nucleated and are 

 classified according to the shape of this nucleus and their 

 affinity for certain stains, but they vary somewhat. They are 

 known as leucocytes, and those which take up foreign particles 

 are phagocyctes. Those which stain with basic dyes such as 

 methylene blue arc known as basophil, whilst those which 

 stain with acid dyes such as eosin are termed eosinophil. X 

 verv general classification of the white corpuscles is poly- 

 morphous, with lobed, or multipartite nuclei ; lymphocytes, 

 with large nucleus and little protoplasm ; hyaline, with some- 

 what, similar nucleus, but more surrounding protoplasm ; 

 eosinophil, with large granules staining deeply with eosin ; and 

 basophil, staining with methylene blue. 



E. G. W. (Hull). — Many objects, especially botanical 

 subjects, can be cut quite satisfactorily by hand. The object 

 is held between the finger and thumb, the index finger being 

 curved round the tip of the thumb and held horizontally so as 

 to form a support for the razor. The object may beheld in a 

 piece of pith or even cork. Inexpensive hand microtomes can 

 be purchased from any of the instrument makers if necessary, 

 and in these the object is wedged with pith or cork, or in a 

 piece of carrot. The knife should be drawn steadily from 

 heel to toe with a drawing or slicing movement, the cut being 

 towards one. It should he dipped frequently in water or 

 spirit and water, and effort should be made to cut thin sections 

 rather than complete ones. Most objects cut much better if 

 previously hardened in methylated spirit. 



[Communications and inquiries on Microscopical matters arc invited, 

 and should be addressed to F. Shillington Scahs, "Jersey," 

 St. Barnabas Road, Cambridge.] 



