Rev. C. 8. Lyman on the Auroral Bow of June, 1852. 61 
the broad line in the figure. Hence, 
if both observers saw the same belt, 
and the apparent width was, at each 
place, that stated above, the belt could 
hot possibly have been either of a cyl- 
indrical form, or a flat band lying hor- 
zontally. The only possible form to 
meet the observed conditions, must be 
that of a curtain or thin sheet of auro- 
ral light, seen more or less edgewise 
by the different observers, and making 
an angle with the perpendicular as rep- 
resented in the diagram. ‘This angle, 
in the case before us, must, as is ob- 
vious from the fignre, be nearly equal 
id 18°. Now this so nearly coincides 
With the inclination of the dipping nee- 
dle, (73° with the horizon at New Ha- 
ven,) that it may fairly be presumed 
the belt is under the same magnetic 
conditions as the ordinary streamers 
whic ide in di 
are known to coincide in di- —N, New dei 
fection with the lines of magnetic Angle SNA, 72° 
ei: sad 1 « -SNC,74°. 
} indicated by a freely sts- « SWA,6I°. 
_— needle. On this presumption, Nhigtatoe. = viets 
sec : o 1 ¥ Base N . i ¥ “Tagiee 
© Section of the bow, represented by Scale, 120 miles to an inch. 
® heavy line in the figure, is drawn 
With an inclination of 73° to the horizon. Of course, at N 
faven it must have been seen edgewise, and the visual lines 
tou ung what appeared to be its northern and southern edges, 
“Ned, More properly speaking, its northern and southern Jaces, 
and thus limited not its width but its thickness. Supposing 
this to be the true form and position of the belt, and that the co- 
not far from 150 miles, the perpendicular distance of its 
lower edge above the earth being about 140 miles, and that of 
"S Upper edge about 280 miles. — 
ra The conelnsion of Dalton respecting auroral beams, (Meteor- 
ology, 1834, p. 165, Prop. 5,) is interesting in this connection, Viz.: 
that, “The distance of the beams of the aurora from the earth’s 
Surface, is eqnal to the length of the beams, nearly.” He appears 
‘9 have considered the rainbow-like arches or belts, as a distinet 
‘etomenon from the ordinary beams; though in some manner 
Connected with them. He it is very probable they are 
