Sun Viewing and Drawing. 439 



at first be only very faintly indicated with the lead pencil in 

 the drawing, and then the Chinese white applied after the 

 drawing has been gummed down. The object in using tinted 

 paper as the foundation, is in order that the facube may be 

 the more plainly apparent, by contrast. 



But there is another point of much importance, which 

 should be attended to by any one who is making a study of 

 solar phenomena ; and that is, a good approximation at least 

 to the ever- varying apparent positions of the sun's poles and 

 equator. Otherwise it would be impossible to determine 

 whether any group of spots or other phenomena were situated 

 in the sun's northern or southern hemisphere — a matter this 

 of much interest. For it is by no means the case that the top 

 or apparent zenith point of the sun's disc is always his north 

 pole, or the bottom or nadir point is always his south pole. 

 In fact, not only has the solar pole a proper inclination of his 

 own of about 7° to the plane of the earth's ecliptic, but in 

 consequence of the perspective effects produced partly by the 

 earth's revolution in her orbit, but much more by her daily 

 rotation on her own axis, the sun's poles (as referred to our 

 horizon) are never the same for two minutes successively, save 

 at about the hours of six a.m. and six p.m. ; as the writer 

 first discovered for himself, with no little interest. Or again, 

 whilst at noon, in England, the sun's north pole in autumn 

 lies many degrees to the left of his zenith, it lies just as far to 

 the right of it at noon in spring. Thus it is always shifting. 

 How then is this knotty point to be ascertained ? How can 

 we declare where his north and south poles lie, bathed in their 

 landmarlc-less incandescent ocean of light? 



With an equatoreally mounted instrument this would be a 

 comparatively easy matter, but we are supposed now not to be 

 in possession of such a luxury. But any ordinary telescope 

 may be readily furnished with a thin slip of semi-transparent 

 mother-of-pearl about the sixteenth part of an inch in width, 

 graduated off into divisions the tw^Ii of an inch apart (every 

 fifth and tenth graduation made more conspicuous, as before) ; 

 and having also an exceedingly fine wire stretched across it in 

 the middle at right angles, and the whole inserted within the 

 focus of your terrestrial eye-piece. When viewing the sun 

 therewith by direct vision, the position of any solar spot may 

 be laid down with sufficient accuracy for most purposes, by 

 throwing the fine wire exactly in a line with the zenith and 

 nadir points of the sun for the time being, and then, whilst it 

 is in this position, bringing up the mother-of-pearl to the centre 

 of the spot, and counting how many graduations it lies to the 

 right or left of the wire ; then upon revolving your eye-piece in 

 its screw about ninety degrees (and so bringing the wire into 



