TRANSACTIONS OP THE SECTIONS. 7 



this is to account for the rays and rifts, it would be rash to deny that it may do so in 

 some manner yet to be discovered. It is quite certain that some of the plienomena 

 observed just at the beginning and end of totality are really caused by it. A light 

 haze of meteoric dust between us and the moon might give results much resembling 

 those observed ; but when we come to details this theory seems to be doubtful. 



Here photography steps in to pave the way out of the existing doubts. If the 

 rays and rifts were reaUy atmospheric, it would hardly be possible that they should 

 present the same appearance at different stations along the line of totality ; indeed 

 they would probably change their appearance every moment, even at the same 

 station. If they are cislunar, the same appearances could not be recorded at 

 distant stations. It is universally admitted that proof of the invariability of these 

 markings, and especially of their identity as seen at widely separated stations, 

 would amount to a demonstration of their extraterrestrial origin. Eve-sketches 

 cannot be depended on ; the drawings made by persons standing side by side differ 

 often to an extent that is most perplexing. Now photogi-aphs have, undoubtedly, 

 as yet failed to catch many of the faint markings and delicate details ; but their 

 testimony, as far as it goes, is unimpeachable. In 1870, Lord Lindsav at Santa 

 Maria, Professor Winlock at Jerez, Mr. Brothers at Syracuse, obtained pictures 

 some of which, on account partly of the unsatisfactory state of the weather, could 

 not compare with Mr. Brothers's picture obtained with an instrument of special 

 construction*; but all show one deep rift especially, which seemed to cut down 

 through both the outer and inner corona clear to the limb of the moon. Even 

 to the naked eye it was one of the most conspicuous features of the eclipse. Many 

 other points of detail also come out identical in the Spanish and Sicilian pictures ; 

 but whatever doubts may have still existed in regard to the inner corona were 

 finally dispelled by the pictm-es taken in India, in 1871, by Colonel Tenuant and 

 Lord Lindsay's photographic assistant, Mr. Davis. 



None of the photographs of 1871 shows so great an extension of the corona as is 

 seen in Mr. Brothers's photograph, taken at Syracuse in 1870 ; but, on the other hand, 

 the coronal features are perfectly defined on the several pictures, and the number of 

 the photographs renders the value of the series singulariy great. The agreement 

 between the views, as well those taken at different times during totality'' as those 

 taken at different stations, fully proves the solar theory of the inner corona. "" We have 

 in all the views the same extensive corona, with persistent rifts similarly situated. 

 Moreover there is additional evidence indicated by the motion of the m'oon across 

 the solar atmospheric appendages, proving in a similar manner as in 1860, in re- 

 ference to the protuberances, the solar origin of that part of the corona. 



It will be well here to mention a difficulty which occurs in recording the fainter 

 solar appendages, namely the encroachment of the prominences and" the corona 

 on the lunar disk when the plates have to be overexposed in order to bring out 

 the faint details of the corona. It is satisfactory to find that whenever a difficulty 

 arises it can he mastered by proper attention. ~ Lord Lindsay and Mr. Ranyard 

 have successfully devoted themselves to experiments on the subject. They tested 

 whether reflections from the back surface of the plate played any part in the 

 production of the fringes : for this purpose plates of ebonite and the so-called non- 

 actmic yellow glass were prepared : and it wa.s immediately found that the outer 

 haze had completely disappeared in the photographs takein on ebonite, while on 

 the yellow glass plates it is much fainter than on ordinary white glass plates. 

 By placing" a piece of wetted black paper at the back of an unground plate, the 

 outer haze was greatly reduced; but by grinding both the back and the front sur- 

 faces of a yellow glass plate, and covering the back with a coating of black varnish, 

 it was rendered quite imperceptible, thus showing the greatest part of the so-called 

 pliotographic irradiation to be due to reflection from the second surface. 



* Mr. Brothers had,, in 1870, the happy idea to employ a so-called rapid rectilinear 

 photographic lens, made by Dallmeyer, of 4 inches aperture and 30 inches focal length, 

 mounted equatorially, and driven by clockwork ; and he was followed in this matter by 

 both Col. Tennant and Lord Lindsay in 1871. The focal image produced, however, is far 

 too stiiall (Jij cf an inch, about) ; therefore it will be desirable in future to prepare lenses 

 of siiuilar construction, but of longer focal length and corresponding aperture. 



