Decembeb 10, 1909] 



SCIENCE 



855 



in parallel with the arc. Besides the usual ex- 

 periments, the existence of a large number of 

 harmonics may easily be shown by means of 

 resonance. The current in the neighborhood 

 of the discharge is much greater than that 

 taken from the mains, owing to the conver- 

 sion of direct-current into alternating-cur- 

 rent energy. For these experiments an e.m.f. 

 of at least 400 volts, alternating, or better 

 direct, is necessary. 



Walter G. Cady 



MiDDLETOWN, CONN. 



SOCIETIES AND ACADEMIES 



THE AMEEICAN PHILOSOPHICAL SOCIETY 



Bailey's Comet: C. L. Doouttle. 



The return of Bailey's comet in 1910 has nat- 

 urally been looked forward to with great interest 

 by astronomers and others. For the purpose of 

 encouraging investigation of the circumstances of 

 its return, a prize of 1,000 Marks was offered by 

 the Astrononxisclie GeseUschaft in 1904. A very 

 complete discussion of the available data was 

 carried out by P. H. Cowell and Andrew C. D. 

 Croramelin, of Greenwich. It has been referred 

 to in various places under the motto, " Isti miran- 

 tur stellam." The prize was awarded to this 

 discussion. 



As soon as the region where the comet was 

 expected to be found had emerged from the sun's 

 rays in 1908, search was undertaken, photograph- 

 ically, in this country and Europe. This was con- 

 tinued until the sun's rays again interfered, but 

 without result. On resuming the process during 

 August of the present year, impressions were 

 found on several plates, the first to achieve suc- 

 cess being Dr. Wolf, of Heidelberg. He first 

 detected the image on a plate taken August 28, 

 but did not venture to announce his discovery 

 until September 11. Two plates were taken at 

 Greenwich on September 9. At first nothing was 

 found on either, but a reexamination after- 

 wards showed faint images of the comet on 

 both. It is barely possible that a reexamination 

 of the plates taken last winter may show faint 

 images of the comet, but nothing has been an- 

 nounced up to the present time. It is now easily 

 visible with the 18-inch telescope of the Flower 

 Observatory. The ephemeris of Messrs. Cowell 

 and Crommelin at the time of discovery required 

 a correction of 25 seconds in right ascension and 

 4 minutes in declination, which must be consid- 



ered remarkably satisfactory when we remember 

 that the last observations at their disposal were 

 made nearly seventy-four years ago. The time of 

 perihelian passage, given in this discussion, seems 

 to require the correction of 3.4 days, which makes 

 the date April 20, 1910. Another examination of 

 this point gives for the date April 18.63. The 

 nearest approach to the earth will be May 19, dis- 

 tance about 14,000,000 miles, but it will then be 

 so near the sun that it will probably not be visible. 

 On May 18.14, Greenwich mean time, the earth 

 and the comet will be in heliocentric conjunction. 

 It is not unlikely that, on this date, the earth 

 will pass through the tale of the comet. The date 

 when it will be visible to the naked eye is quite 

 uncertain, but probably it will be bright enough 

 for this purpose some time during February, when 

 it will be seen in the western sky after sunset. 

 Toward the end of March, after passing the sun, 

 it appears in the morning before sunrise, reaching 

 its greatest apparent distance from the sun early 

 in May. Toward the middle of May, it again 

 passes the sun and reappears in the evening sky. 

 Halley's investigation of this comet forms an 

 epoch in astronomical history, but it must be 

 confessed that considerable courage on his part 

 was required to make the prediction of its 

 return in 1759. Probably if he had been aware 

 of the uncertainty attending the identification, 

 depending on the period alone, he would hardly 

 have ventured to make it. Examination of an- 

 cient records indicates a succession of visits, ex- 

 tending back to 240 B.C., with the very consid- 

 erable range of a little more than five years 

 between the longest and shortest period. With 

 such a range some of these supposed appearances 

 must be regarded as resting on rather slight 

 foundation. A committee appointed by the As- 

 tronomical Society has formulated a plan for 

 keeping the comet constantly in view, by interest- 

 ing a series of observers, so placed in latitude and 

 longitude that the comet shall never be lost sight 

 of. A series of photographs, taken in this way, 

 giving a continuous history of the comet, should 

 go far toward solving a number of problems con- 

 nected with the physical behavior of these bodies. 



the BIOLOQICAL society op WASHINGTON 



The 461st meeting was held November 13. 1909, 

 with President Palmer in the chair. Tlie follow- 

 ing communications were presented: 



The History of the Mule-footed Hog: W. J. 

 Spillman. 



