January 1, 1898.] 



KNOWLEDGE 



no vertical line on the rostral shield. The ground colour 

 is soft red, brown, or grey, with dark, angular, black-edged 

 spots, very elegantly arranged. 



In brilliancy and harmony of colour it is, perhaps, the 

 most beautiful of the Ancistiodou, though 1 prefer the 

 more sober copperhead ; and it is probably the most 

 venomous. An acquaintance of mine brought a very bad 

 account of the rhiKliistdmn from -Tava, to which island it 

 appears to be confined; and Dr. Gunthtr relates that Kubl 

 saw a man succumb to the bite in a very few minutes, but 

 I can find no record of any experiments with the venom. 

 In this respect the liilinniiKx, which also lives under 

 the line, may be a possible rival ; but, as I have said, 

 I can get no information — that is, reliable information — 

 on the point. The peculiar virulence of the venom of 

 the I liodoxtomK , which is not by any means a large 

 snake, is rather remarkable, as the majority of the East 

 Indian pit-vipers do not appear to be very dangerous. 



I have only suggested the lines for a rough-and-ready 

 "recognizer," which might be applied to any family of 

 serpents. At the same time I can as^sure those who are 

 interested in ophidians that a more minute study of this 

 or any other genus, will well reward the student ; and that 

 during its pursuit they wUl naturally and easily become 

 acquainted with those more striking featiujes which I have 

 endeavoured to illustrate. 



THE PRISMATIC CAMERA DURING TOTAL 

 ECLIPSES. 



By Wji. Shackleton, f.r.a.s. 



NOW that the last eclipse of the century is close 

 upon us, and at nearly every observing station a 

 prismatic camera is to be employed, it may be 

 interesting to give a brief account of some of the 

 results which the revival of its use during total 

 eclipses has elicited for us. Just in the same way that 

 Fraimhofer's method of 

 observing stellar spectra 

 has been applied to photo- 

 graphing the spectra of 

 stars with amazing results, 

 so the same method of 

 placing a prism in front of 

 the telescope and observ- 

 ing the sun when totally 

 eclipsed has, with the aid 

 of photography, given 

 equally important infor- 

 mation. 



The prismatic camera 

 as used during eclipses is 

 simply an ordinary camera 

 (with a lens of from two 

 inches aperture and up- 

 wards) in front of which 

 is placed one or more 

 prisms, so that, instead 

 of photographing the sun 

 directly, the light has first 

 to pass through the prism, 

 which differentiates the 

 composite light of corona, 

 prominences, and chromo- 

 sphere mto the many 



monochromatic images of which it is composed; and if 

 sutiicient dispersion be used these are so separated as not to 

 interfere with each other, but are perfectly distinct. 



The advantages of using this slilltss spectroscope over 

 one with a slit during a total eclipse is self-evident, for 

 by it all the phenomena round the dark moon can be 

 analyzed at once with a maximum aperture, whilst in the 

 case of an ordinary spectroscope only the small portion 

 which the slit crosses can be brought under observation. 



That this is a desideratum one may see when it is 

 remembered that it is only possible by intermittent glances 

 to observe the eclipsed sun for about two hours in a life- 

 time. Fortunately, however, the chromosphere and pro- 

 minences, which were enigmas for nearly two centuries, 

 have, since the discovery of Lockyer and Janssen in 1868, 

 been possible to observe and photograph without an eclipse. 

 \Yhen we come to the corona the story is a sadder 

 one, for it must have been observed from the time of 

 primeval man ; indeed, we have hieroglyphical records of 

 it by the ancient Egyptians and Babylonians, and yet we 

 know least of all about this the greater bulk of the sun. 

 Hence the prismatic camera, for giving us a large survey of 

 its chemical constitution, is again the most advantageous 

 instrument to employ. 



Not only for quantity, however, but for quality also, is 

 it paramount. When photographs are taken with a sht 

 spectroscope it is really the slit that is being photographed, 

 and any Ught, no matter how it reaches there, is what is 

 being investigated. Generally an image of the particular 

 part that is required to be studied is focussed on the sht by 

 a condensing lens, and this gives the principal effect : but 

 besides this there is a general illumination from all 

 the other parts, for the light from these is scattered 

 and reflected by minute dust particles in our atmosphere, so 

 that in addition we have the integrated light from these 

 superposed on what we wish to investigate, and, of course, 

 the brightest of these extraneous sources gives the greatest 

 additional effect. 



In the case of the prismatic camera, however, it is only 

 the real images of the eclipsed sun that are focussed on the 

 photographic plate, and the general illumination of the 



Prismatic Camera, used in Brazil. 



atmosphere, although equally passing into the camera, has 

 no definite outline, and therefore no image can be formed ; 

 so it is more scattered still by the prism, and only goes to 



