Variation of the Star C.P.D. - 41°-4511. 



37 



mean light curve of 1901, July 1 and 2. These reduced observations 

 are as follows : — 



Reduced Date. 



Mag. 



Reduced Date. 



Mag. 



Reduced Date. 



Mag. 





1901. d. h. m. 



m. 





1901. d. h. m. 



ni. 





1901. d. h. m. 



m. 



1. 



July 1 1 12 



10-00 



33. 



July 1 20 50 



10-00 



64. 



July 2 13 45 



10-00 



2. 



2 3 



10-00 



34. 



21 14 



9-90 



65. 



13 48 



10-05 



3. 



2 15 



10-00 



35. 



22 10 



9-90 



66. 



14 50 



10-25 



4. 



2 33 



1000 



36. 



22 57 



10-00 



67. 



15 5 



10-35 



5. 



2 45 



10-00 



37. 



23 10 



10-00 



68. 



15 5 



10-40 



6. 



2 45 



9-90 



38. 



1 23 20 



10-00 



69. 



15 12 



10-45 



7. 



4 6 



10-00 



39. 



2 10 



10-00 



70. 



15 15 



10-40 



8. 



5 25 



10-00 



40. 



1 50 



9-90 



71. 



15 20 



10-55 



9. 



5 55 



1000 



41. 



2 45 



10-00 



72. 



15 25 



10-60 



10. 



6 25 



1000 



42. 



3 



10-00 



73. 



15 35 



10-60 



11. 



6 30 



10-00 



43. 



4 15 



10-00 



74. 



15 35 



10-75 



12. 



7 



1000 



44. 



4 52 



10-00 



75. 



15 40 



10-60 



13. 



7 44 



10-00 



45. 



5 25 



1000 



76. 



15 50 



10-70 



14. 



9 36 



10-00 



46. 



6 25 



10-00 



77. 



15 50 



10-85 



15. 



9 45 



10-00 



47. 



6 30 



10-00 



78. 



15 55 



10-75 



16. 



10 



10-10 



48. 



7 5 



10-00 



79. 



16 



10-85 



17. 



10 



10-00 



49. 



7 26 



10-00 



80. 



16 5 



10-75 



18. 



10 58 



10-00 



50. 



7 30 



10-00 



81. 



16 15 



10-95 



19. 



13 30 



1000 



51. 



8 15 



10-00 



82. 



16 30 



10-90 



20. 



13 45 



10-00 



52. 



8 42 



10-05 



83. 



16 30 



10-85 



21. 



14 30 



10-10 



53. 



9 15 



10-05 



84. 



16 45 



10-80 



22. 



15 



1000 



54. 



9 30 



9-90 



85. 



16 48 



10-95 



23. 



15 58 



10-00 



55. 



10 15 



10-00 



86. 



17 



10-65 



24. 



16 



10-00 



56. 



10 30 



10-00 



87. 



17 



10-60 



25. 



17 



10-15 



57. 



11 30 



10-00 



88. 



17 15 



10-45 



26. 



18 



10-15 



58. 



11 42 



9-90 



89. 



17 15 



10-6S 



27. 



18 30 



1000 



59. 



12 15 



10-00 



90. 



17 30 



10-30 



28. 



19 



10-05 



60. 



12 48 



10-10 



91. 



17 45 



10-25 



29. 



19 



10-00 



61. 



13 10 



9-90 



92. 



18 



10-15 



30. 



20 



10-00 



62. 



13 20 



10-20 



93. 



18 15 



10 15 



31. 



20 



1010 



63. 



2 13 40 



10-10 



94. 



2 19 30 



10-05 



32. 



1 20 44 



10-00 















From these observations the following elements of light variation 

 can be readily determined : — 



Full period of variation Id. 20h. 30m. 3s. 



Epoch of prin. min 1901. July 2d. 16h. 17m. 



Epoch of second, min July Id. 17h. 30m. 



Magnitude at max lO'OOm. 



Magnitude at prin. min. 10"90m. 



Magnitude at second, min 10* 15m. 



Duration of prin. mid 4h. 30m. 



Duration of increasing phase... 2h. 15m. 



Duration of decreasing phase... 2h. 15m. 



The explanation of Algol variation which has commended itself to 

 astronomers generally, is that every Algol variable is a binary star, 



