6o 



THE GUIDE TO NATURE 



telling of something comet-like." 



No. This is not a magazine of the 

 "Oh, my !" museum order, hut of "com- 

 monplace nature with uncommon in- 

 terest." Altair need not he more em- 

 phatically specified than Antares or 

 hundreds, yes, thousands of other 

 stars that have been shining for ages — 

 and as continuously as humanity's 

 good things that have come not 

 periodically hut without intermission 

 from above the stars. May they shine 

 on evil becoming less and less, and on 

 appreciation ever increasing. If you 

 have missed their heauty and con- 

 tinued beneficence, all the greater your 

 misfortune and the more urgent is the 

 necessity that you hasten to make 

 amendment of your thoughtless ways. 

 All hail, then, astonishing, beautiful, 

 permanent Altair, and all others that 

 rise in the east or circle the north. 



The Heavens in June. 



BY PROF. ALFRED MITCHELL, OF COLUM- 

 BIA UNIVERSITY. 



When this is read, the most brilliant 

 period of Halley's Comet for the year 

 1910 will be a thing of the past, and the 

 ".omet will be each night becoming 

 fainter and fainter. After it first ap- 

 peared in the morning skies, it did seem 

 as if we were to be doomed to disap- 

 pointment for pi ess dispatches of the 

 comet being without tail were heralded. 

 In spite of these ominous warnings, the 

 comet appeared as a magnificent object 

 in the morning skies, as the majority of 

 readers well know, from having seen it 

 with their own eyes. The interested 

 amateur in looking to find it has learned 

 a little of the disheartening trouble of a 

 professional astronomer's life, the inter- 

 ference in work caused by clouds. As 

 many readers know from bitter experi- 

 ence, it needed a deal of enthusiasm to 

 get up morning after morning in the 

 hope of seeing the comet, and then be- 

 hold nothing for their pains but a bank 

 of clouds. Bad weather throughout the 

 country interfered greatly with observa- 

 tions in the morning skies, but putting 

 together the reports from different ob- 

 servatories, we find that the comet was 

 not in the least a disappointing one, and 



it was just as remarkable as we had 

 expected Halley's Comet to be. It has 

 not been at any time as supurb an object 

 as the great comet of 1XN2. which in 

 turn was not as magnificent as the 

 comets of 1861 or 1858. 



For the benefit of those who saw the 

 comet and estimated the length of the 

 tail, we give some reliable data for ascer- 

 taining its length. As is well known, the 

 astronomer measures the angular length 

 by the number of degrees subtended at 

 the eye by two lines running out to the 

 object to be measured. With a little 

 practice it is as easy to estimate the 

 angle in degrees as it is to guess at the 

 height of a fence in feet. For obtaining 

 a value of small angular distance, it is 

 well to remember that the sun and moon 

 are each a little more than half a degree 

 in diameter. The distance between the 

 extreme stars in the belt of Orion is 

 close to three degrees. A more useful 

 measure (since it may always be seen) 

 is the angle between the pointers of the 

 Dipper, which is a little more than five 

 degrees. Though the tail was invisible 

 on April 12 (mainly from being seen in 

 a dawn-lit sky), a tail of 1° was seen on 

 April 15, of 9° on the 18th, which had 

 increased to 15° by the last day of April. 

 On a photograph taken by Professor 

 Barnard on the morning of May 5, the 

 whole extent of tail was 20°. On May 

 13 a naked eye view of the comet from 

 New York City showed it to have a tail 

 at least 35° in length. If this had been 

 pointing straight up from the horizon, 

 it would have stretched more than one- 

 third of the way to the zenith. The tail, 

 though faint, was clearly visible, spread- 

 ing out in a fan-shape till it stretched 5° 

 across at the end of the tail. It was a 

 magnificent sight, with the morning star 

 Venus close by and very brilliant, and 

 those who saw a comet for the first time 

 will long remember this one. 



Though the angular diameter of the 

 sun and moon are about the same their 

 real diameter in miles are very much 

 different because the moon is so much 

 nearer us. In the same way the length 

 of the tail in miles may be ascertained 

 when we know the distance in miles that 

 it is from us. Earlv in May the tail 

 was 25,000,000 miles 'long. 



The prevalence of superstitious fear 



