456 



KNOWLEDGE. 



November. 1910. 



AN ALMOST FORGOTTEN BINOCULAR DEVICE. 

 — .'Vs many readers of " Knowlkdge " still use that most 

 excellent but discredited instrument, the stereoscopic bin- 

 ocular, it may be worth while to bring to their remembrance a 

 simple yet almost fortjotten de%'ice. now more than a ijuarter 

 of a century old, which certainly improves the image. 



If one of the eye pieces is removed and the back of the 

 object glass is examined, when a full cone is used, it will 

 appear as in Figure 1. Generally the iris below the substage 

 condenser is somewhat closed, and the appearance seen is 

 like Figure 2. If now. instead of closing the iris, a stop of the 

 form Figure 3, be inserted underneath the substage condenser, 

 the back of the object glass will appear like Figure 4 in each 

 tube, and a much improved picture of the object will be 

 obtained. 



o 



Some little care is required in making this double hole in 

 the stop of a proper si^e. The best procedure is to experiment 

 with stops cut out of cardboard, and when the right effect is 

 obtained to have it copied in brass. Of course it will be 

 necessary to have a special stop for each objective, and to 

 remember that it can only be used with the substage condenser 

 for which it was made — this, however, is a minor difficulty 

 which can be readily oxercome. 



Some years ago I made expei'iments by placing at the back 

 of the object glass a stop having two circular apertures, as in 

 Figure 3, but with larger holes ; since then experience has 

 shown that nothing much is gained by doing this ; the improve- 

 ment seems to depend entirely- upon the stop ;it the back of 

 the substage condenser. 



Great care must be taken with the illumination, so that it 

 appears the same in both holes when viewed at the b.ick of 

 the object glass, the eye pieces being removed for that 

 purpose. 



In general, the best illumination for transparent objects, 

 when a stereoscopic binocular is used, is obtained by focussing 

 the image of the flat of the flame upon the plane of the object, 

 of course without a bull's eye. 



Edward M. Nelson, F.R.M.S. 



For the purpose of producing duplex illumination for the 

 binocular instrument Kiddell made use of two mirrors, and 

 Stephenson a duplex stop with cylindrical lenses. It was 

 in 1892 that Mr. Nelson first suggested the use of the 

 above described stop in conjunction with the achromatic 

 condenser. — [A. W. S.J 



VAMPYRHLLA LATERITIA Li: IDV.—While engaged 

 in an exploration of the Sikkim Himalayas my friend. Dr. 

 Kellas, made his camp for several daj's near a small lake 

 called the Green Lake, at an altitude of nearly sixteen 

 thousand feet. From this lake he very kindly obtained for 

 me a small quantity of mud. As the " mud " consisted of a 

 coarse glacial detritus, one could hardly imagine less promising 

 material for examination. However, on placing some of this 

 mud in a large specimen-tube and allowing it to remain for a 

 few days. I was agreeably surprised to find I had a small 

 collection of the living micro-fauna from this Himalayan lake. 

 As the material was quite free from putrefactive bacteria, the 

 organisms remained alive for some weeks. Besides several 

 infusorians there were two bdelloid rotifers, which Mr. Da\ id 

 Pryce kindly named for me i they were Ph iliuhiia aciiticoni is 

 Murray and CaUidina clcf^ans Milne, both, as I understand, 

 recorded from Scotland. But my first and only acquaintance 

 with the Rhizopod named at the head of this paragraph, was 

 from this material. It is recorded by Cash, from Cheshire, 

 and by Professor West, from North Wales, but it certainly 

 seems of interest to find it high up in the Himalav'as. 



fn the first tube I examined I found several actinophrvs-like 



organisms, the protoplasm of which was coloured a bright 

 orange. This was recognised as \'ainpyrcUa lateritia from 

 the description and figures in Cash's British Rhizopods (Ray 

 Society's Publications). It appears to have been first 

 described by Cienkowski in 1863. under the name 

 VampyrcUa spirogyrac, but Professor Leidy has shown 

 reason for considering that Fresenius had described it under 

 the name Aiiiochn lateritia in 1856. hence this specific name 

 takes priority over spirogyrac. Professor Leidy. in Tlic Fresh- 

 water Rhizopods of A^ortli America, in 1879, describes the 

 'granular protoplasm as pervaded with colouring matter of 

 different shades of orange. The periphery of the body is 

 hyaline, and it is surrounded by pseudopodial rays giving it 

 an actinophrys-like form." The pseudopodia are further 

 described as being " of two kinds, the ordinary delicate, 

 straight rays and pin like rays ending in a minute round head." 

 .■\s the specimens had travelled from India in an encysted 

 condition, my observations were carried out under adverse 

 circumstances — since they never really attained a state of 

 active metabolism. The pin-head appearance of certain of 

 the pseudopodia seemed to be the effect of refractive granules 

 passing outwards along the threads of protoplasm. It is very 

 possible the small lake from which the specimens came was 

 so named from some filamentous alga w hich coloured it green. 

 This also would be the food of V. lateritia which feeds on 

 the chlorophyll of such algae as spirogyrae. I was, of course, 

 unable to observe its method of feeding, but there seems to be 

 some divergence of opinion as to how it is effected. The 

 earlier observers describe the Vampyi"ella as perforating the 

 cell vv.ill of Spirogyra, and thus extracting the chlorophyll. 

 M. Penard adds that in addition to perforation of the cell wall 

 there is a suction action on the part of the Vampyrella. Mr. 

 Cash in the above mentioned book describes and figures a 

 method which differs from that of the other observers. He 

 says the Vampyrella anchors itself by means of its pseudopodia 

 to the terminal cell of a thread of Spirogyra and actually 

 bends this cell luitil it separates from the thread, when it is 

 able to extract the chlorophyll : it proceeds in this way until 

 there are a number of empty separated cells. 



PHOTOeiR.APHY. 



By C. E. Khxxeth Mehs. D.Sc. (Lond.). F.C.S. 



PHOTOGRAPHY BY INVISIBLE RAYS.— Professor 

 R. W. Wood, of The Johns Hopkins University, gave the 

 Thirteenth Traill Taylor Memorial Lecture before the Royal 

 Photographic Society on September 27th. He discussed the 

 methods which he has adopted for photography by the infra- 

 red and ultra-violet rays, and the results obtained. 



Photography by the infra-red requires only plates having 

 sensitiveness in that region and a screen removing .almost all 

 the visible spectrum, and permitting only rays of wavelength 

 superior to 7,000 A.U. to pass. These long infra-red, or 

 rather deep red, rays are very little scattered in their 

 passage through the atmosphere, and are almost wholly absent 

 from the light reflected from blue sky, so that by their use blue 

 skies appear very dark, entirely black near the zenith and 

 lightening towards the horizon. Even the lightest clouds 

 become very bright compared with the sky, so that the method 

 seems well adapted for the study of faint cloud forms in 

 meteorology. Vegetation, on the other hand, has but little 

 absorption in this region of the spectrum and reflects the 

 light plentifuUv, so that trees appear snow-white against the 

 black skv. 



The photographs in the ultra-violet were taken by means of 

 a quartz lens silvered until it was opaque to ordinary light. 

 Such a silver film transmits light between the wavelengths 

 3,000 and 3,200 A.U.. by which light the photographs were 

 produced. 



These ravs are scattered so powerfully by the atmosphere 

 that the air always appears to be full of haze; the general 

 appearance of landscapes in clear bright sunshine being 



