April, 1902.] 



KNOWLEDGE. 



81 



the ilisturbt?d area in the ooroua observed on the eclipse 

 negatives : — 



Suu-spot 



Apex of Coronal Disturbance 



Position angle. 



60-2 

 600 



During the period of eleven days covered by the photo- 

 ifniphs only this one group of spots was visible. In this 

 time almost the entire solar surface wtis under observation. 



We see from the above position angles that this region 

 of sun-spots occupied the same line of sight as the apex 

 of the disturbed coronal region. While it is true that we 

 have no means of determining the exact position of 

 the coronal disturbance in the line of sight, attention 

 was called in Bulletin No. 9 to the probability that 

 its origin was near the Sun's limb. As both sun- 

 s[>ot and disturbance are shown to have the same latitude, 

 it can hardly be doubted that this unusual ajipearance 

 in the corona was in reality immediately above the 

 group of sun-spots and faeulije, and that it had its 

 origin in the same disturbance of the Sun's surface. 

 The long, thread-like prominence to the south, seen pro- 

 jected almost tangentially from the Sun's surface, appears 

 likewise to have emanated from the same group of spots 

 and faculae. 



These observations furnish very strong evidence of the 

 intimate connection of all solar phenomena. Sunspots, 

 faciiliP, prominences and corona all seem, in the present 

 case at least, to have had a common origin. 



The appearance of this disturbed region in the corona 

 and its undoubted connection with the group of spots on 

 the surface so strongly suggested great activity that an 

 investigation was mad'e as to whether there had been a 

 measurable displacement of any of the coronal, masses in 

 this region. The interval of time between photographs 

 of the corona available for this purpose was but little over 

 five minutes, yet if the velocities were large, 50 or 100 

 miles per second, such motion should be easily detected. 

 The results give no certain indication of motion in the 

 interval. The uncertainties of measurement of these 

 coronal masses is so large, however, that a velocity of .5 or 

 10 miles per second would not be detected in so short an 

 interval of time. We may conclude that the velocity 

 across the line of sight was less than 20 miles per second 



The interval of one and one-half hours between the 

 times of the eclipse in Mauritius and Padang should 

 render a comparison of negatives secured at these two 

 stations valuable in this connection. 



C. D. Peerine. 



THE USE OF HAND TELESCOPES IN 

 ASTRONOMY. 



Bv Cecil Jackson. 

 III.— THE PLANETS. 



Mercury. — This planet is practically beyond the 

 reach of very small telescopes. It appears very small 

 even in a 3-inch telescope. The crescent phase might 

 be glimpsed with a power of 80 on a 2-inch instrument. 



Venus. — The crescent phase of this planet may be 

 distinctly seen with a power of 30 or 40 on a 

 H or 2-inch telescope. A pocket telescope with a good 

 magnifying power will just show the crescent, especially 

 if the lens next but one to the eye-end be removed. 

 Owing pai-tly to the great brightness of the planet, and 

 partly to its great distance from the earth at the time 

 of the gibbous phase, this latter phase is not well seen 

 in hand telescopes of ordinary power. With a power 

 of 80 this phase would be visible. 



Mars. — The marking of this planet will barely be 

 distinguished in a 2-inch hand telescope, even if the 

 instmment is fitted with an astronomical eye-piece, but 

 its small red disc may be distinguished with a power 

 of 30 or 40, and may be seen with a pocket telescope at 

 a favourable opposition of the planet. 



Jupiter. — The disc of this planet may be seen at 

 any time when the planet is visible. The four chief 

 satellites discovered by Galileo in 1610, ai-e readily 

 observed in a li-inch telescope. The smallest satellite 

 was not discovered till 1892 at the Lick Observatory 

 by Prof. Barnai'd. and is visible only in two or three 

 of the largest telescopes in the world. 



Fig. 7 is a sketch of Jupiter, as seen with my l|-inch 

 telescope at about 8h. 56m. p.m., July 13, 1899. An 

 astronomical eye-piece was used. Jupiter's belts are 

 not conspicuous in a l?.-inch telescope. The satellites 

 form sometimes a striking group. Two seen close 

 together make a pleasing view. 



Saturn. — A power of 30 diameters will show the 

 wonderful ring system surrounding this planet. The 

 crape ring, however, cannot be seen with any telescope 

 so small as two inches in apertui-e. The two bright 

 rings will be seen as one. A 2-inch instrument is too 

 small to show the division between them. 



Fig. 8 gives an idea of the appearance of Saturn, as 

 seen with the ring widely open, on Aug. 30, 1899. 

 Power 30 on the l|-inch telescope was used in making 

 this sketch. With a pocket telescope, Saturn simply 

 appears as an oval disc, the dark sky between the ball 

 and the ring being invisible, except perhaps with an 

 extra high power on the instrument. Uranus and 

 Neptune are, for all practical purposes, beyond the reach 

 of even 2-inch telescopes. The disc of Uranus might be 

 just made out with such a glass by comparing it with 

 a small star. 



RECENT OBSERVATIONS OF MARS. 



By E. M. AxTONiADi, f.e.a.s. 



The question of objective change on Mars, beyond the 

 obvious formation and dissipation of the polar snows, has 

 long been tlie battleground of modern areography. For 

 years and years such change was denied, and, indeed, the 

 old observations of surface modifications were too rough 

 to be able to carry conviction. Based, however, on a priori 

 considerations, which were not in harmony with experience, 

 the arguments of the unbelievers were destined to fall in 

 the long run, their defenders having departed from the true 

 course of enquiry — induction, based on acute observation. 

 Change evidently implies, here, as elsewhere, the 

 action of some sort of energy, and, especially, radiant 

 energy ; such energy coming either from the planet itself 

 or from the sun. That the planet's crust derives no 

 appreciable quantity of heat from the interior, is amply 

 demonstrated by the presence of snow at the poles. The 

 snow forms, imchecked, in winter, extending down to 



