May 4, 1905I 



the second the distribution and forms of prominences 

 round the limb. To obtain the latter, a metal disc 

 iust a little smaller than the solar image is placed 

 close up to the primary slit plate (Fig. 2), and re- 

 tained there by a metal wire fixed to a firm base ; this 

 disc is so adjusted that it is concentric with the solar 

 image While in use it becomes extremely hot, and 

 it is therefore necessary that it be made of metal and 

 riveted to the wire which supports it. These limb 

 pictures, an example of which is given in Fig. 3, are 



NA TURE 



Without entering into too minute details, the follow- 

 ing brief summary of the more salient facts derived 

 from a general survey of the photographs taken 

 during the past year may be given. , c * • 



Dealing with the " disc " pictures in the hrst in- 

 stance, all of them show a " mottling " of very 

 definite character extending from the equator to the 

 poles. Nearer the equatorial regions this motthng 

 seems to become exaggerated in size in patches, some 

 of the interspaces becoming filled up, giving rise to 



Fig. 3. — Limb and disc of ; 



' K" lijht, July 19 Limb exposed 

 to iih. 5im. 485. (interval 



of a composite nature in that after the exposure of 

 the limb has been made the metal disc is removed 

 from the primary slit, and a " disc " exposure is 

 made on the same plate. It has been found by ex- 

 perience that a " limb " exposure requires^about^sixty 

 times the time that is necessary for a " disc " ex- 

 posure. Under verv favourable conditions fifteen 

 seconds is necessary 'for the latter and fifteen minutes 

 for the former 



NO. 



,853, vol. 72] 



the prominent flocculi, many of which clearly indicate 

 the mode of structure. Fig. 3 gives an idea of their 

 appearance in the photographs. It will_ be seen that 

 there are frequently long streaky bright portions 

 springing apparently from a central nucleus and 

 having subsidiary ramifications. A three-legged form- 

 ation 'is a very common type of structure in many ot 

 the photographs. . 



These flocculi, in the first instance, exist alone, but 



