/ 
ON THE TOTAL ECLIPSE OF THE SUN, MAY 28, 1900. 407 
Edwards’ snap-shot Isochromatic plates were iised throughout, and the expedition 
is greatly indebted to Messrs. Edwards for supplying special batches of plates on 
patent j^late glass. 
A few of the plates were developed at Santa Pola, and the remainder were 
developed at the Solar Physics Observatory, pyro-soda developer being used. 
Description of Fhoto<jrap)hs. {Plate 6.) 
The photographs indicate the same succession of phenomena recorded in the three 
previous eclipses, but the recent eclipse was specially advantageous, for the reason 
that the chromospheric arcs at the instant of contact were of greater lengtli. 
Taking the 20-foot series as typical of both, we find the following general 
appearances in the ten photographs :— 
(1.) “ Instantaneous ” exposure 2 seconds before beginning of totality. Chromo- 
sj^heric arcs in great numbers, those corresponding with hydrogen, calcium (H and 
K), and lielium being of great length ; the whole crossed longitudinally by streaks 
of continuous spectrum from the uneclipsed j^hotosjfiiere. A number of small 
prominences are shown on the H and K arcs, and less strongly on the arcs due to 
hydrogen and helium. The arcs, like the continuous spectrum, are broken up by the 
irregularities of the moon’s limb. 
(2.) “Instantaneous” exj^osure, at (or just before) beginning of totality 
(Plate 6, a). Plate almost identical witli No. 1, hut with fewer streaks of continuous 
spectrum. 
(3.) “Instantaneous” exposure 2 seconds after beginning of totality. Some¬ 
what similar to No. 2, but without marked continuous S23ectrum from the jihoto- 
sj^here. There is a general shortening of chromosj^heric arcs, more esjjecially notice¬ 
able in those which are shortest in Nos. 1 and 2. 
(4.) “Instantaneous” exjiosure 4 seconds after beginning of totality. Nothing 
now visible but a comjDaratively small number of arcs due to the upper chromos|)here. 
Chief among these are H and K, H/3, Hy, &c., of the liydrogen series, Dg and other 
arcs due to helium, and others due to strontium, iron, &c. Plate under-exjiosed. 
(5.) Exjiosed from 6 to 12 seconds after beginning of totality. The increased 
ex^josure at tliis stage has had the effect of increasing the intensity of the chi'omo- 
spheric spectrum as compared with No. 4, the arcs now l:»eing nearly as numerous a.a 
in No. 3, but relatively less intense. A notable feature is the relative increase 
in the intensity of tlie lines of helium and the line 4687, to which reference was made 
in the report on the Indian eclijjse. 
Fragmentary rings due to the corona ajopear on this plate, tlieir 2 >osition-angles of 
maximum intensity being quite different from those of tlie chromosphere and 
iwominences. The brightest ring is that in the green, X 5303'7, but others are also 
distinctly seen. 
