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THE GUIDE TO NATURE 



from this time its apparent motion 

 westward became very rapid, so that it 

 reached D by November 1, and was 

 soon afterward lost in the rays of the 

 sun. 



The path followed by this little 

 comet is smaller than any other known 



Figure 2. An attempt was made to photog.aph the 

 comet at D. 



comet's orbit. It is so flattened that 

 when the comet is at A. Figure 2, it 

 is but 3.000,000 miles from the sun and 

 when it is at B it is 380,000,000 miles 

 distant; three-fourths of the distance 

 of Jupiter. On October 27, when the 

 comet was nearest the earth, it was at 

 C, and was then but 27,000,000 miles 

 away. It reached the point A, nearest 

 the sun on December 5. The comet 

 completes the circuit of its orbit in 

 three and one-third years. 



When photographed in September, 

 the comet was found to be fainter than 

 the fourteenth magnitude, and hence 

 only visible in the very largest tele- 

 scopes. Even when nearest us in Oc- 

 tober, it appeared merely as a round, 

 faint , nebulous patch, with a thin, 

 thread-like tail, the object being very 

 much too faint to be seen with the 

 naked eye. The true diameter of the 

 comet at this time was about 150,000 

 miles. 



The interest of this small and incon- 

 spicous comet arises wholly from the 

 fact that it is peculiarly disturbed by 

 some unknown cause in the course of 

 its journey around the sun. Instead of 

 making its circuit with perfect regular- 

 ity as all other known periodic comets 

 do, it is continually moving faster and 

 faster. From 1819, when it was dis- 

 covered, until i860, it arrived at each 



return about two and one-half hours 

 ahead of time ; during the next ten 

 years it gained one and three-fourths 

 hours at each evolution and at present 

 each period is about two hours shorter 

 than the preceding one. Altogether, 

 it has gained in this way about fifty- 

 six hours since its discovery. 



Whatever it is that disturbs the mo- 

 tion of this little cloud, it is probably 

 met with while the comet is pursuing 

 that part of its orbit which is most 

 remote from the sun. It is here that 

 the zone of little planets known as 

 asteroids are found, and it is possible 

 that beside the hundreds of these bod- 

 ies which we can see there may be in 

 this region of the Solar System a band 

 of asteroidal dust, through or near 

 which the comet passes at each revo- 

 lution. 



When the comet was last at the 

 point D, Figure 2, very nearly at its 

 greatest distance from us, an attempt 

 was made to photograph it with the 

 very powerful reflecting telescope at 

 Mount Wilson. California. After long 

 exposure, an object resembling the 

 comet was found on the plate, so that 

 we now have strong grounds for the 

 hope that, after this, the position of 

 the comet among the stars can be pho- 

 tographed at successive points entirely 

 around the orbit. It will then at once 

 appear whether the observed disturb- 

 ance is produced suddenly, and if so 

 in what part of the orbit the disturb- 

 ance occurs. This will go a long way 

 toward removing the mystery of the 

 unseen disturbing body whose effects 

 have for so long a time been a puzzle 

 to astronomers. 



The Stars in January. 

 This month witnesses the entrance 

 of the brilliant Leo. the last of the win- 

 ter groups, into our evening sky. This 

 will be found low in the east, its bright- 

 est star, Regulus, forty light years dis- 

 tant from us, marking the end of the 

 handle of the beautiful Sickle, which 

 bv May becomes so prominent an ob- 

 ject in the evening skies. 



South of the Sickle, the head of the 

 Water Snake will be seen emerging 

 from the ground, though the long body 

 will not be fully risen in the early 

 evening until next May. Still farther 

 south is the brilliant Sirius, thirteen 

 times as bright as Regulus, while 



