February 21, 1890.] 



SCIENCE. 



133 



cott's New Series of Eeadei's," by Eben H. Davis, superintendent 

 of schools, Chelsea, Mass. (complete in four books; the third 

 and fourth readers in press) ; ' 'How to Remember History, ' ' a 

 method of memorizing dates, with a summary of the most im- 

 portant events of the sixteenth, seventeenth, eighteenth, and 

 nineteenth centuries, for the use of schools and private students, 

 by Virginia Conser Shaffer ; ' 'A System of Oral Surgery' ' (fifth 

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 ti'eatise on the diseases and surgery of the mouth, jaws, face, 

 teeth, and associate parts, by James E. Garretson, surgeon in 

 charge of the Philadelphia Hospital of Oral Surgery, dean of the 

 Philadelphia Dental College, etc. ; "Chambers's Encyclopaedia, " 

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 the Rev. E. Cobham Brewer, Trinity College, Cambridge, author 

 of "The Reader's Hand-Book," "Dictionary of Phi-ase and 

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LETTERS TO THE EDITOR. 

 Mock Sun. 



The train leaving Albany for Boston, in surmounting the 

 hills east of the Hudson River, affords the traveller very beau- 

 tiful views of the wide valley, the river, and a picturesque sky- 



line formed by the bold and broken Helderbergs. On the 

 evening of the 9th this view was enhanced in beauty by a 

 superb sunset, having seemingly the double glory of two suns 

 twenty degrees apart. It was not easy to determine the actual 

 sun, so brilliant were both reality and counterfeit; but the 

 mock sun, like many pretenders, overdid the thing a little, 

 and assumed very gorgeous rainbow effects, that are not seen 

 very near the royal original. It was north of the actual sunset. 



The pretender was not, however, the often seen "sun-dog,"' 

 which is ordinarily a scrap of rainbow color, but it had a 

 luminous centre of golden refulgence, that was worthy of the 

 orb of day ; and, when seen by shutting off the sun with a 

 shade, it made a centre of a brilliant sunset, really holding a 

 court of its own. 



This most attractive phenomenon, with varying changes, all 

 wonderful, lasted for nearly half an hour, affording, in connec- 

 tion with the remarkable views, a very unusual unison of 

 terrestrial and celestial beauty. The change of our point of 

 view was five or six miles as the train sped on ; but the thin 

 clouds upon which the colors were so lavishly embroidered 

 were very far away, not showing perceptible change in position 

 relative to the sun with that movement of the observer. 



The same phenomena were simultaneously observed at Caze- 

 novia, one hundred and ten miles due west, but there the sun's 

 rival was seen south of the great luminary. 



The next day was clear and fine at Cazenovia, but snowing 

 at Boston, indicating that the frost crystals that masqueraded 



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