VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 539 



Such for instance would be those, if true, recently described in the 

 Newspapers, as being much complained of by our army at Suakin on the 

 Red Sea; viz., a temperature in the shade of 110°, and a depression of the 

 Wet bulb of 4° or 5° only; which implies no less than 20 grains of water-gas to 

 every cubic foot of air ; and wo aid present a subject of observation to any 

 earnest spectroscopist of perfectly phenomenal attraction, — if Government would 

 only condescend to make it possible to him, by granting commissariat facilities 

 of transit to, and lodging at, the place. 



Part VII. — Results arrived at touching true Solar Lines in 



THE YEAR 1884. 



It is now time, however, to return to our own more immediate subject ; 

 viz., the hard and fast lines of Solar origin in the Solar spectrum. Lines which 

 every one, in every country and in all varieties of climate sees, or should see, as 

 constant as the Sun itself. And yet some anomalies occasionally will, and do, 

 occur, when even such lines have to be observed and tabulated by human 

 agency. So that an important business before us now, is to ascertain by fact, 

 whether the method here adopted, of publishing three successive and indepen- 

 dent spectra in final juxta-position with each other, and with two previous 

 authorities, has any real advantage in clearing up some of those otherwise 

 doubtful, perhaps inscrutable cases, which will now and then happen among 

 even the latest and most carefully taken observations. 



Thus at 44,620 W. N. Place, or on Plate 25, a strong line, far outside any 

 water-gas variation effect, and represented both by M. Fievez's, and the 2nd and 

 3rd Winchester, Spectra, is not contained in the 1st Winchester Spectrum. So 

 that had that view alone been published by me, it might have led to time- 

 wasting discussions on a supposed lost line of the Solar Spectrum, vanished 

 between 1882 and 1884 ; when the simpler, and I believe the true, explanation 

 is, that the omission was merely an accidental slip on my part of one line in 

 6000, occurring at the Jii'st, but not on the two succeeding occasions. 



On Plate 43, however, we find in M. Fievez's spectrum no symptom 

 whatever of a very strong line, also far above water-gas variation limits in that 

 part of the spectrum (viz., 53,673 W. N. Place), although it is conspicuously 

 and solidly recorded on each of the three Winchester spectra. 



Wherefore, if the Belgian Astronomer maintains the truth of his negation 

 of that strong line's existence when he observed in 1882 ; and if neither he, nor 

 any one else can disprove that there must have been such a line there when I 

 observed in 1884 ; and, without any prepossession in favour of such a thing did 

 on three independent occasions, separated from each other by two or three 

 weeks, — always record a nearly first class line, whose position was subsequently 



