Astronomy. 225 



out of its course, and then mixing up wdth the light of the chro- 

 mosphere, give us a sort of continuous spectrum, with the hydro- 

 iren bright lines superposed upon it ; in other words, that as the 

 • v.. perceives a bright, irregular region or glare around the un- 

 ' I'X'tl sun, an effect due to our atmosphere, so also the eye might 

 ni' a bright, irregular region or glare around the uneclipsed 

 "'■■sphere durimj eclipses, due also to our atmosphere. 

 ' 'n' word here about the CUiromosphere, the name I have given 

 ■ I in- bright-line-giving region outside the photosphere. It has 

 1"!il: been clear that the spectroscopic method of observing it when 

 ti"' sun is not eclipsed is not totally effective; that is to say, that 

 Hf only see a percentage of it— perhaps only a relatively small 

 i't ivt'iitage~but the glowing prominences, that is, those in which 

 " ' ', I'" t • ii], lue of the rapid motion of ejection from the s 



CO at all angles from the line of sight, afford 

 [)robably a layer of cooler hydrogen suscep- 

 d visible above the ordinary level. Now as 



'i:^i 



high, it is not unreasonable t 

 . -^ -...u t.nr umuinospnere may even extend to that distance, or 

 ^\^'H a little beyond it. 



llenoe it was that in the Instructions to Observers, drawn up by 

 ^"■ot. ^>tokes, and myself, and approved bv the organizing com- 

 °^' ' t!,?'" ?^^ 1870 eclipse, it is stated that— 



iPAL OBJECT to be obtained is to determine whether 

 o differentiate the outer lavers of irregular outline 

 ^n-s (of the corona) from a 'stratum, say some 5' or 

 High round the sun, which mav possibly be the limit of the 

 aseous envelopes above the photosphere." 

 ihe spec:troscopic observers, therefore, were enjoined— 

 • io determine the actual height of the chromosphere as seen 

 ith an eclipsed sun; that is, when the atmosphei 



enect of which is doubtless only partially got ..^ .— 



f isMii-Lockyer method, is removed. If the method were totally 

 i^<, the C line, the line of high temperature, should hardly 

 ."' ,1" height : but there can be little doubt that the method ia 

 :;'lly effective, so the increase in height should be carefully 



f' uiid^tl' ,*^^^*^!""^^"? ^^ ^here exists cooler hydrogen above and 

 A, 1 XI Vividly incandescent layers and prominences." 

 Andthepolarisers— ^ ^ 



L detached and selected part of the corona about 



,f«7i"ggotsofar, 



1 attack, namely, tf 



i.n„ ^ ^y*^ oljservations, the spectros^copic method, under c 



polari 'n?"'^*^"''''''' "^%lit have been by far the most doubtful, tlie 

 Po^nscope method coming next. 



^^' U<rht !!f '^^*^ *^ ^^^ spectroscopic observations, if we assume that 



^l^e obsp -^^'^^ ^^ received l>y and from our own atmosphere, 



ervations would be easily translated. A pure contmuous 



