1894.] Results with Prismatic Camera during Eclipse of Sun. 7 



II. " Preliminary Report on the Results obtained Avith the 

 Prismatic Camera during the Total Eclipse of the Sun, 

 April 16, 1893." By J. NORMAN LOCKYER, C.B., F.R.S. 

 Received February 22, 1894. 



(Abstract.) 



Daring the total eclipse of 1871 observations were made by 

 Respighi and the author with a spectroscope deprived of its colli- 

 mator, and a series of rings was seen corresponding to the different 

 rays emitted by the corona and prominences. A similar instrument, 

 arranged for photography, was employed during several succeeding 

 eclipses, but the photographs were on so small a scale that none of 

 the results came up to the- expectations raised by the observations of 

 1871. As the Solar Physics Committee is now in possession of a 

 prismatic camera of 6 inches aperture, the prism having a refracting 

 angle of 45, it was determined to employ it during the eclipse of 

 1893. The instrument was placed at the disposal of the Eclipse 

 Committee by the Solar Physics Committee, and was entrusted to 

 Mr. Fowler, who took the photographs at the African station. 



It also seemed desirable that a series of similar photographs 

 should be taken at another point on the line of totality, even though 

 an equally efficient instrument were not available. A spectroscope 

 with two 3-inch prisms of 60, used in conjunction with a siderostat, 

 accordingly formed part of the equipment of the expedition to Brazil, 

 and was placed in charge of Mr. Shackleton. 



The present preliminary report is intended to indicate the kind of 

 results obtained, and some of the photographs are reproduced for the 

 information of those specially interested, as it will be some time 

 before the complete reductions are ready for publication. 



At the African station 30 plates were exposed, 15 during totality, 

 and the remainder in the five minutes before and after totality. In 

 Brazil 17 plates were exposed during totality, and 7 out of totality. 



The most conspicuous lines, or rather portions of circles, seen in 

 the photographs taken during totality, are the H and K lines of 

 calcium, and in these rays the images of the various prominences are 

 very clearly outlined. 



The lines of hydrogen, extending far into the ultra violet, are also 

 very prominent, and numerous other lines are seen in addition. 



Isochromatic plates were used for some of the exposures, and on 

 some of these the ring formed by the characteristic line of the coronal 

 spectrum (1474 K) is clearly depicted, especially in the Brazilian 

 photographs. A comparison with the photographic records of the 

 corona shows that the prismatic camera has picked out the brightest 



