274 



Mr. \V. Brennand. 

 Fio. 3. 



by which it can tarn round OS as an axis, and if one of the planes 

 MOS, IOS be brought to coincide with the plane of symmetry, tl 

 other will coincide with the plane of the Sun's altitude. 



I take a small square (diagram 3) of sensitised paper and cut 

 along CO ; then, slipping the part COB under AOC, so that B coil 



DlAGKAM 3. 



