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Photographic Observations of Morehouse's Comet. 



By W. A. Cogshall. 



Comet c 1908 was found on a plate taken at the Yerkes Observatory 

 on September 1st and. has been so situated as to allow observation from 

 any point in the northern hemisphere for several hours each night. 



Most of the comets, during the time they are visible to us, are in 

 nearly the same direction from us as the sun, and so are seen only for a 

 short time before sunset in the evening, or before sunrise in the early 

 morning. 



Comet c had a high northern declination when found, and afterward 

 passed within about 16 degrees of the north pole of the sky, so that during 

 this time it was visible all night. As a result continuous records were 

 secured through several hours, from the time it became dark in Europe 

 till daylight in California. 



These records show beyond doubt what has been indicated by several 

 other comets — that the tail is composed of matter driven off by the action of 

 the sun from the head of the comet, and that the velocity of motion of these 

 particles in the tail is such that practically a new tail is formed each day. 



While this comet was not very bright visually, it photographed very 

 quickly, exposures of an hour with a short focus lens showing from 6 

 degrees to 10 degrees extension of tail, and it also showed unusual and 

 sudden changes in the details of its tail. 



The most prominent of these are shown in the accompanying photo- 

 graphs. 



The first of these happened on September 30th. The photograph of 

 September 29th shows nothing unusual in the appearance of the comet, 

 but the next plate whose mid-exposure time was September 30th, 11 hours, 

 shows a great change in the size, direction, and general character of 

 the tail. This change began during the afternoon of September 30th, and 

 by early morning following had produced the appearance shown in the 

 plate of September 30th, 14 hours, 45 minutes. 



The great cloud-like mass of tail moved away from the head of the 

 comet at a rate of about 20 miles per second, and on the next evening 



