230 Curious Astronomical Fact. 



castle-upon-Tyne. In this paper the author shows that in a 

 series of observations on Mars, taken with good instruments 

 used in north and south latitudes, the probability of error is 

 very small ; and as the synodical revolution of Mars takes 

 place in about 780 days, that planet will be 23 times in op- 

 position before the next transit of Venus on the 8th December 

 1874. Hence he infers that if careful corresponding observa- 

 tions are made on each of those 23 oppositions, the probable 

 error would be reduced nearly 4'796 times. The author con- 

 cluded his paper by describing what he regards as the best 

 means of carrying this method into effect. 



A new annular Micrometer by Frauenhofer was submitted 

 to the inspection of the Meeting by Mr. Francis Baily : but 

 as this instrument is described at page 177 of our present 

 Number, it is unnecessary to give any further account of it in 

 this place. 



XXXVIII. Intelligence and Miscellaneous Articles. 



CURIOUS ASTRONOMICAL FACT. 



r I ""HE eighth volume of M. Bessel's Observations (for the year 

 ■*• 1822) is arrived in this country. In the preface to that work 

 there are recorded some singular facts relative to the habits 

 of observing, by different astronomers ; which we consider 

 worthy of particular consideration. It is known to our astro- 

 nomical readers that in the Greenwich observations for 1795, 

 page 339, Dr. Maskelyne has the following remark : " I think 

 it necessary to mention that my assistant, Mr. David Kinne- 

 brook, who had observed the transits of the stars and planets 

 very well, in agreement with me, all the year 179+, and for a 

 great part of the present year (1795) began, from the begin- 

 ning of August last, to set them down half a second of time 

 later than he should do, according to my observations : and 

 in January of the succeeding year (1796), he increased his 

 error to 8 tenths of a second. As he unfortunately conti- 

 nued a considerable time in this error before I noticed it, and 

 did not seem likely ever to get over it, and return to a right 

 mode of observing, — therefore, though with reluctance (as he 

 was a diligent and useful assistant to me in other respects), I 

 parted with him." Dr. Maskelyne then proceeds to state the 

 manner in which the discordancies were discovered, and points 

 out some useful hints to those who are much engaged in this 

 branch of practical astronomy. 



M. Besscl 



