January 29, 1904.] 



SCIENCE. 



i(;3 



Yerkes Observatory, noted a large and dis- 

 tinct spot in Kronocentric latitude 36°.5. 

 This was observed mierometrically on 

 June 27 and July 13. 



Acting upon the request of the author, 

 micrometrie observations of spots on 

 Saturn were made by Professor S. W. 

 Burnham with the 40-inch Yerkes equa- 

 torial. Measurements were secured on 

 July 29 £Lnd August 15. Prom these data 

 the 'mean' rotation period deduced was 

 lO*" 38™ 27^ ; but the observations showed 

 the period to be variable. The value 

 W 38™ 18^ + M X 0M856 was found to 

 satisfy all the observations with a mean 

 error of ± 0™.8. In the formula n is the 

 number of rotations of the planet counting 

 from the epoch of the discussion, June 

 23, 1903. 



An Extension of the Group Concept: Dr. 

 Edward Kasner, Columbia University, 

 New York. 

 Read by title. 



Facilities for Astronomical Photography 

 in Southern California: E. L. Larkin, 

 Director of Lowe Observatory. 

 Attention was called to the fact that, 

 from May 1 to November 1, the observer 

 upon Echo Mountain enjoys an almost un- 

 broken succession of cloudless days and 

 nights. During the greater part of this 

 season the air becomes remarkably steady 

 shortly after sunset; so much so that the 

 rings of Saturn may be seen rising as a 

 minute but sharply defined arch over the 

 crest of the neighboring mountain ridge. 

 In the rainy season, after a shower, the air 

 is of such transparency that mountains 

 distant a hundred miles or more may be 

 seen with clearness and distinctness. 



In view of these conditions Mr. Larkin 

 urged the establishment of an observatory 

 equipped for astro-photography upon the 

 summit of Echo Mountain. Attention was 

 called to the faint nebulous light forming 



the background of large regions of the sky 

 as observed from this station. Some inter- 

 esting views of Lowe Observatory and its 

 surroundings were projected upon the 

 screen, together with a number of the 

 famous Lick Observatory photographs. 



Coincident Variations: Lucinus S. McCoy, 

 Whitten, Iowa. 

 Eead by title. 



On the Generalization and Extension of 

 Syloiv's Theorem: Dr. G. A. Miller, 

 Stanford University, California. 

 Dr. Miller's paper, which will shortly 

 be printed in full, is in abstract as follows : 

 Let p" be the highest power of p M^hich 

 divides the order of a group ((?), and sup- 

 pose that a subgroup (P^) of order p" 

 contains only one subgroup (Pg ) of order 

 p^ and of a particular type. It is proved 

 that the number of subgroups of G which 

 are of the same type as P^ is of the form 

 1 -j- kp, and that all of these subgroups 

 form a single conjugate set. Hence the 

 order of G is of the form p^ h^{l -}- kp) 

 where p^h^ is the order of the largest sub- 

 group of G which transforms P^ into 

 itself. By letting /9 = a we have Sylow 's 

 theorem. "When ^ ^= a the factor h^ is not 

 divisible by p while it is divisible by p for 

 all other values of /S. Some simplifications 

 of the proof of Frobenius's extension of 

 Sylow 's theorem are also considered. 



The Supporting and Count er-iueighting of 



the Principal Axes of Large Telescopes: 



C. D. Perrine, Lick Observatory, Mt. 



Hamilton, California. 



In large telescopes it is necessary to 



reduce the friction of the axes in their 



bearings. This has usually been done by 



a system of friction wheels held against 



the a:sis by weights and levers. 



Experience with the roller bearings used 

 in the driving-clock for the new mounting 



