96 Chronicles of Science. [Jan., 



searches is a refractor, 3|- inches in aperture, equatorially mounted, 

 by Lohmeyer, of Hamburg. We have not space to describe in full 

 the various arrangements adopted by Dr. Pihl to secure accuracy. 

 Our readers will probably be more interested in learning that, as far 

 as the researches have yet gone, there would seem to be indica- 

 tions of movements having taken place since the epoch of Bessel's 

 measurements. The mean declination of seven stars exammed by 

 Bessel is 4" 27 south of the mean dechnation as now observed. 

 " Is it probable," says Dr. Pihl, " that this difference is owing to 

 errors in observation or reduction, and to no physical change ? " 

 This is a question which cannot be answered until the com-se of 

 time enables astronomers to obtain some satisfactory e\ddence re- 

 specting any process of change which may be going on. 



A remarkably interesting paper is supplied by Mr. Stone, on the 

 subject of the observations made upon the transit of Venus which 

 took place in 1769. Our readers are doubtless aware that the 

 estimate of the sun's distance, which has so long found a jDlace in 

 our treatises of astronomy, was founded upon those observations. 

 When other methods of determining the sun's distance had led to 

 results differing by three or four millions of miles from the value 

 hitherto received, astronomers were somewhat at a loss to understand 

 how it was that so faulty a value should have resulted from a series 

 of observations so elaborate, and apparently so successful, as those 

 which were made upon the transit of 1769. It will be remembered, 

 that the calculation of the sun's distance had been managed by Encke, 

 and there seemed every reason for supposing that he had spared no 

 pains to treat the observations which came under liis hands in the 

 most careful and satisfactory manner. An attempt was made by 

 Powalky to show that the observations of the transit could be made 

 to agree with modern determinations of the sun's distance. But, 

 according to the opinion of the best mathematicians, Powalky 

 allowed himself far too great freedom in selectmg the materials he 

 made use of. Professor Newcombe, of Ameiica, had been more 

 successful in representing the observations of 1769. Still, however, 

 there was considerable discordance. 



It appeared to Mr. Stone that a new discussion of the observa- 

 tions of 1769, if made with due care, would neces.-arily lead to a 

 clearer view of the sources of systematic error, or wrong interpreta- 

 tion which might be feared and ought to be guarded against, in 

 the observations proposed to be made of the transits of 1874 and 

 1882. In the course of his investigations he was led to the detec- 

 tion of several grave and fundamental errors, which had iireviously 

 been made in the discussion of the observations of 1769, and to a 

 value of the solar parallax, entitled to be received with confidence. 



The great difficulty lies in the i'act that at the moment of true 

 internal contact Venus does not present the appearance of a cucular 



