TO KNOW THE STARRY HEAVENS 



281 



One very interesting method of esti- 

 mating the distance of certain of these 

 clusters is made possible by the cir- 

 cumstance, known for many years, that 

 a large number of their stars are varia- 

 ble in brightness. These belong to a 

 definite class of variables known as the 

 Delta Cepheid variables, so called be- 

 cause the star Delta of the constella- 

 tion Cepheus (shown at A, Fig. 1) is a 

 typical and conspicuous example of the 

 class. These stars increase quite sud- 

 denly to maximum brightness, then 

 diminish more slowly and irregularly, 

 and then brighten again, the whole pe- 

 riod being so short as a few days or 

 even as a few hours. 



Such a kind of variation can only 

 occur in stars of a quite definite physi- 

 cal condition and inherent brightness, 

 especially if the period is about one- 

 half a day, a type very common in 

 clusters. By comparing the apparent 

 brightness of these stars with the ap- 

 parent brightness at a known distance, 

 the distance of the cluster at once fol- 

 lows. 



Thus in the well-known, though 

 rather faint little cluster in the constel- 

 lation of the Hunting Dogs (at B, Fig. 

 1) the average brightness of no vari- 

 ables was found to be 15.5 magnitude, 

 the average deviation of separate stars 

 from this being 0.08 magnitude, thus 

 indicating clearly how uniform the real 

 brightness of these objects is. Simi- 

 larly in the cluster in Centaurus the 

 average magnitude was 13.57 (that is, 

 6.25 times brighter) from which we 

 conclude that the first cluster is 2.5 

 times as far away as the second. 



A recent interesting investigation is 

 upon the probable ages of these spheri- 

 cal clusters ; that is, upon the time 

 which would be required for a rather 

 irregular cloud of stars of such vast 

 dimensions to acquire an approximate- 

 ly spherical form. Basing the mathe- 

 matical investigation upon what seem 

 to be reasonable assumptions in regard 

 to the size and average distance apart 

 of the stars, the required time is found 

 to be no less than two thousand million 

 years. Truly our conceptions of dis- 

 tance and of duration have been enor- 

 mously extended during the past few 

 Years ! 



The Things I Love in Nature. 



It is strange perhaps to think of, but I 

 never cared for flowers, 

 With their tints of pink and purple, blue 

 and red; 



But the things I love in nature are the 

 height, the depth, the length 

 Of the mountains and the ocean and the 

 plain, 



Oh, I love to see the mountains with their 

 everlasting snow, 

 And the things too big and fine to under- 

 stand, 

 Like the huge and mighty cataracts where 

 waters ever flow, 

 And the limitless expanse of desert sand. 



And the forests and the jungles, and the 

 desert, and the plain, 

 Where the colors always mix and never 

 clash, 

 For there's nothing bad in nature, nothing 

 ever small or mean, 

 Ev'rything is always good and square 

 and strong; 

 And there's nothing looks untidy, ev'ry 

 place is pure and clean, 

 And there's no mistakes, and nothing's 

 ever wrong. 



Oh, I love to lie at midnight in the clean 

 and open veld, 

 And to watch the stars above me in the 

 sky; . . . 

 It is good to be out somewhere all alone 

 in Nature's arms, 

 When one lays one's blanket down and 

 goes to rest; 

 And I've often thought of all her gifts, of 

 all of Nature's charms, 

 That the glory of her silence is the 

 best. . . . 



— Brian Brooke, in "The Christian Science 

 Monitor." 



Winter. 



These Winter nights against my window- 

 pane 



Nature with busy pencil draws designs 



Of ferns and blossoms and fine spray of 

 pines, 



Oak-leaf and acorn and fantastic vines, 



Which she will make when summer comes 

 again — 



Quaint arabesques in argent, flat and cold, 



Like curious Chinese etchings. 



T. P. Aldrick— "Frost-Work." 



"We love things not because they are 

 beautiful, but they are beautiful be- 

 cause we love them." 



Every pleasant glance we give to the 

 realities around us, with intent to learn, 

 proceeds from a holy impulse, and is 

 really songs of praise. What differ- 

 ence can it make whether it take the 

 shape of exhortation, or of passionate 

 exclamation, or of scientific statement? 

 These are forms merely. Through 

 them we express, at last, the fact that 

 God has done thus or thus. — Emerson. 



