57 



THE POPULAR SCIENCE MONTHLY. 



them. In Europe the weather was generally 

 bad. Good observations were made, how- 

 ever, at Potsdam, Prussia. The reports so 

 far received from the southern hemisphere 

 are most gratifying ; and, whatever it may 

 be with the stations yet to be heard from 

 (chiefly near the Straits of Magellan), 

 '' enough is already secure to make it cer- 

 tain that we have observations sufficient in 

 number and character to test the full value 

 of the transit as a means of determinimr 

 the solar parallax." It must be several 

 years, however, before the observations can 

 be fully reduced and published, and the 

 exact results ascertained. 



Work cf the Dearborn Observatory. 



The great equatorial of the Dearborn Ob- 

 servatory, Chicago, was employed during 

 1SS1, under the direction of Professor G. 

 W. Hough, chiefly in the observation of the 

 great comet of the year, the planet Jupiter, 

 the satellites of Uranus, and difficult double 

 stars. A drawing of the nucleus and en- 

 velope of the comet, showing the peculiar 

 formation of the head and surrounding en- 

 velopes, was made on the 23d of June by 

 Professor Colbert, who also first announced 

 the distance of the comet from the earth. 

 In attempting to reconcile the various phe- 

 nomena alleged to have been seen on the 

 disk of Jupiter, the greatest difficulty is 

 found to exist in determining what is real 

 and what is imaginary. Contemporaneous 

 sketches by different persons, or even two 

 by the same observer, show such marked 

 discrepancies that they are of but little use 

 in ascertaining suspected changes. The 

 observations made here during the past 

 three years confirm the statement that the 

 changes on the disk of the planet are slow 

 and gradual. The attempted observations 

 on the inner satellites of Uranus were im- 

 peded by unfavorable night weather. About 

 two hundred and fifty micrometer measure- 

 ments of double stars were made, including 

 nine measurements of the companions of 

 Sirius. Sixty difficult double stars, not 

 found in the catalogues, were discovered, 

 including two quadruple systems and one 

 naked-eye star, with a very minute com- 

 panion. Mr. S. W. Burnham is preparing 

 for publication a catalogue of one hundred 

 and fifty-one double stars discovered at the 



observatory during the past three years ; 

 also, a compilation of all the star observa- 

 tions made by him during the same period, 

 comprising about twenty-five hundred meas- 

 urements. The observatory is open to mem- 

 bers of the Chicago Astronomical Society on 

 Thursday evenings ; and classes from the 

 city high-schools and elsewhere are occa- 

 sionally admitted. 



The Poles of Extreme Cold. There ap- 

 pear to be two districts on the northern hemi- 

 sphere, widely separated from each other, in 

 which the coldest places on the earth are 

 to be found. One is in Northeastern Sibe- 

 ria, the other in the American Arctic Archi- 

 pelago. The particular points within these 

 regions, that have the property of being 

 colder than all surrounding points, may be 

 called the poles of extreme cold. Their 

 geographical situation is not precisely ascer- 

 tained, because a sufficient number of ob- 

 servations have not been made, but enough 

 is known to make it safe to conclude that 

 the Asiatic pole is north of Yakutsk, and 

 the American pole northwest of the Parry 

 Islands, toward Eastern Siberia. The 

 Asiatic pole is upon the mainland, the 

 American pole in a sea studded with isl- 

 ands ; and from this the two regions derive 

 distinct climatic characters. Near the Si- 

 berian pole, which lies in the comparatively 

 low latitude of from 60 to 70, the conti- 

 nental climate is exhibited in an extremely 

 cold winter and a warm summer, while the 

 more maritime climate of the American 

 pole, which lies between 65 and 68 of lati- 

 tude, is expressed in a relatively milder 

 winter and cooler summer. Yakutsk has 

 hitherto been considered the coldest place 

 on the earth, it having a mean temperature 

 in January of 45. Colder places have 

 since been found that have a mean temper- 

 ature for January as low as 55. They 

 are situated in about latitude 67 north, 

 near Werkojansk, in Siberia. The cold-pole 

 is located here from November till March ; 

 it then moves in April and May toward the 

 northwest into the Arctic Ocean, between 

 the mouth of the Obi and Nova Zembla, and 

 afterward returns to Werkojansk. Werko- 

 jansk is the only place that lies within the 

 isotherm of 40 3 during November, De- 

 cember, January, and February, or for four 



