Proceedings of the Royal Society of Edinburgh. 209 
At Aberdeen, the evening of the 5th of April was very favourable for observing 
the Occultation of Jupiter and his Satellites by the Moon, in as far as regarded the 
Immersions. The following are the times of these phenomena, after allowing for 
the error and rate of the clock, which were ascertained by transits of the Sun : 
By Observation. 
By Calculation. 
- 
D. 
H. 
/ 
7/ 
D. 
H. 
/ 
Immersion III. Satellite, 
April 5. 
23 
6 
52,7 
— 
— 
— 
I 
23 
10 
5,2 
First External Contact, 
23 
17 
37,7 
5 . 
23 
17 
2,53 
First Internal Contact, 
- 
23 
18 
40,2 
23 
18 
7,81 
Immersion II. Satellite, 
- 
23 
22 
25,7 
<— 
— 
Second Internal Contact, 
6. 
0 
9 
12,5 
6 . 
0 
8 
51,03 
Second External Contact, 
- 
0 
10 
15,5 
0 
9 
52,83 
The Immersion of the I V. Satellite happened at so short an interval from that 
planet, that it could not be conveniently attended to. The times of the immer- 
sions are supposed to have been obtained to the nearest half second ; but a haze 
which afterwards accompanied the Moon, rendered the Emersions of the Satellites 
invisible, and the two observations of the emersion of the planet subject each to an 
uncertainty of two or three seconds. The telescope used was a 3| feet achromatic 
one by Dollond, with a power of about 70. 
Art. XXIV. — Proceedings of the Royal Society of Edinburgh . 
(Continued from Vol. X. p. 3 53). 
April 5. 1824.— 44 On the Application of Professor Dccbe- 
reiner's late Discovery , to Eudiometryf by Dr Edward Tur- 
ner. (This paper is printed in the present Number of this 
Journal). The same evening there was read a paper 44 On 
the Quartz District in the vicinity of Inverness ,” by Mr George 
Anderson. 
April 19. — -There was read a memoir by Dr Brewster, 44 On 
the Optical and Mechanical Structure of Miner als which form 
the Composite System f which it is proposed to add to other 
Systems of Crystallography. 
May 3.— There was read 44 Conclusion of Dr Turner's Me- 
moir on Eudiometry y At this Meeting, the following gentle- 
men were elected members: 
William Wood, Esq. Surgeon. 
Dr W. C. Mair, Physician to the Embassy to Mexico. 
May 17. — 44 Account of two Surfaces of Siliceous Velvet , in- 
capable of reflecting light , and produced by the fracture of a 
large Crystal of Quartz f by Dr Brewster. 
VOL. XI, NO. 21. JULY 1824. 
o 
