March, 1902.] 



KNOWLEDGE 



61 



is pointing at the sun, and a bright patch of light 

 will appear on the paper. Slide the eye-tube of the 

 telescope inwards until the patch of light has a shai-p 

 outline, and if there ai-e any large spots upon the sun 

 thoy will appear in the Solar image cast on the paper. 

 When once the sun's image has been thrown on the 

 paper, the telescope may be grasped by the left hand 

 in sucii a way as to cast a margin of shadow around tbc 

 image of the sun, or a cai-dboard disc may bo fitted 

 round the telescope tube for the same purpose. This 

 will make the Solar image appear more pronounced. 



More detail can, however, be seen by using a dark 

 glass, and looking directly through the telescope at the 

 sun. On a telescope not excectling two inches in 

 aperture there is no fear of the gla.5S cracking, especially 

 if the sun is not observed when high up in the sky, 

 3S it is at noon in summer, for example. In obsei-ving 

 the sun when high up, it is a good plan to turn the 

 telescope aside ovciy few seconds so as to prevent the 

 dark gla.ss from becoming hot. 



I sliall now begin to describe the details of the sun 

 as seen in the telescope. 



Fio. 4. 



Fig. 4 represents the sun as seen at about Ih. Im. p.m., 

 June 24. 1899. A represents white marking seen near 

 the sun's limb. B is a small spot. C is a lai'gc spot, 

 surrounded by a gi"ey border called a "penumbra " to 

 distinguish it from the dark centre or " umbra.'' My 

 Ig-inch telescope with its own terrestrial eye-piece was 

 used in making this obsei-vation. The pancratic draw 

 was set to the power 30 line, so as to give a magnifying 

 power of 30 diameters. 



Fig. 5 represents the sun as seen on Aug. 5, 1893. 

 Power 35 on the 1 g-inch telescope used. Time, about 

 4h. 9ni. p.m. This picture gives an idea of the sun's 

 appearance when largely spotted. As an instance of 

 the difference in the number of days on which no spots 

 are observed on the sun in different years, I may men- 

 tion that I obsen'ed uo. spots on the sun on eight 



occasions in 1898, whilst in 1899 the days on which no 

 spots were obsei-ved were about thirty-two. 



Fig. 6 represents the sun as seen with a 1-inch pocket 

 telescope at about 2h. 41m. p.m., Friday, Oct. 28, 1898. 

 A dark glass was, of course, used on the telescopy. On 

 very clear days the sun may be seen, if a 2-inch telescope 

 IS used, to have a curdled appearance. I have some- 

 times seen this appearance with my l|-incli telescope. 

 Tapping tho telescope with the fingers, or moving it 

 backwards and forwards may assist to make the curdling 

 visible. 



tttcrs. 



[The Editors do not hold themselveB responsible for the opinions 

 or statement* of correspondents] 



THE FLIGHT OF A HAILSTONE. 



TO THE EDITOKS OF KNOWLEDGE. 



Sirs, — In reference to the interesting paper on " The 

 Flight of a Hailstone," in the February number of 

 Knowledge, I venture to send you the enclosed sketches 

 of some hailstones which fell here on June 13th, 1900. 

 They fell in large numbers at the end of a very severe 

 thunderstorm. The area over which they fell was limited 

 to a few miles radius. In form they resembled a cart- 

 wheel, being thickest at the circumference. The alternate 

 clear and opaque rings were very distinctly marked. The 

 largest measured one and a half inches in diameter, and 

 the weight, after the stones had been lying, perhaps, a 

 quarter of an hour on the ground, was one-third of an 

 ounce. Somewhere about '65, a similar storm of hail 

 occurred in Herefordshire, but the shape of the stones 

 was different, each stone being largest in the centre, and 



Hailstone. — Actual fizc. 



Side view o£ 

 broken stone. 



diminishing to the circumference, resembbng not a cart- 

 wheel but an oyster. Some of the largest of these latter 

 stones weighed an ounce. 



South Leigh Vicarage, Arthur E.\st. 



Witney, O.xou. 



