Royal Astronomical Society. 379 



telescope is one of Fraunhofer's, of three inches aperture, and is 

 very clear. I hear that it was observed at Rome on Sept. 24, with 

 a telescope made by Cauchoix, of eight inches aperture, and that it 

 was extremely faint. I was absent from the observatory from the 

 middle of October to the 31st, on which evening I found it easily 

 between the places given by the two systems of elements, as you 

 inform me Sir J. Herschel saw it in September. At Milan it was 

 observed on Oct. 24. On the last evenings it was very faint and 

 very difficult to observe : in general, the least disturbance of the 

 atmosphere extinguished it entirely." 



II. Various observations made at the observatory of St. Helena 

 by Lieutenant Johnson ; consisting of, 



1. Stars observed with the Moon from March to July, 1832. 



2. Observation of the solstice of June 1832. 



3. Observation of the Solar Eclipse of July 27, 1832. 



III. Investigation of a rule for clearing the apparent distance of 

 the centres of the Sun and Moon from the effects of parallax and 

 refraction. By Charles Blackburn, B.A., late R.M. College. 



In the Monthly Notice for May 1832 is given a formula of Baron 

 Zach for the solution of this problem. The method proposed by 

 Mr. Blackburn is similar in principle, so far as it consists in deter- 

 mining the true distance by the application of certain corrections 

 to the apparent distance j but differs in the manner of obtaining the 

 corrections, which are two in number instead of four. 



IV. Observation of the Transit of Mercury of May 5, 1832. 

 Made at Utrecht, by Professor Moll. 



The author first notices the observations made in Holland at the 

 preceding transits of Mercury in 1661, 1697, 1753, 1799, and 1802, 

 and then proceeds to state the preparations that were made to ob- 

 serve the present transit. A table contains the result of the obser- 

 vations. 



" Even with such small powers as 64 and 76 of the achromatic 

 telescopes of Fraunhofer and Dollond," Dr. Moll observes, "1 could 

 plainly perceive a grayish spot on the dark disc of Mercury. As 

 soon as I had perceived it, I asked my assistants whether they saw 

 any thing particular on Mercury. One of them instantly replied, 

 ' Do you mean the white spot V On applying higher powers (as 1 1 

 and 180 to the 42-inch, and 96, 144, 216, and 324 to the 6-feet,) 

 the same appearance was always visible. Its periphery was not 

 well defined, but seemed gradually to sink from a grayish white to 

 the dark colour of the planet's disc. It constantly appeared on the 

 same part of the disc. 



" After the observation, looking in Schroder's Hermographic 

 Fragments, I was much surprised to find that both Schroder and 

 Professor Harding had observed a similar appearance during the 

 transit of 1799. They even attempt a delineation of the object, in 

 which there are two separate spots. I cannot say that I saw any 

 thing resembling this, as it seemed to me and others that there was 

 one grayish undefined spot on the black disc of Mercury. 



" I must not here omit the circumstance, that this gray spot was 



3C2 



