19S Scientijic Intelligence. 
terruptiony except at the moment of her inferior conjunctiemy and 
four days before and after it. Mr Dick considers day observations 
as of great utility, in ascertaining whether or not Venus has an at- 
mosphere, as Schroeter supposes ; and he suggests the propriety of 
employing them, with the view of discovering if any planets exist 
in the immense interval of 37 millions of miles between Mercury 
and the Sun. In making day observations, Mr Dick has al- 
ways found, that the opaque screen which is used to intercept 
the direct rays of the Sun, produces an effect corresponding to 
its distance from the object end of the telescope. 
OPTICS. 
2. Distant VisihilUy of Mountains. — The following observa- 
tions on the distance at which mountains have been seen possess 
considerable interest : 
Himalaya Mountains, 
Mount Ararat from Derbhend, 
Mowna Roa, Sandwich Isles (53 leagues), 
Chimborazo (47 leagues) 
Peak of TenerifFe from South Cape of Lanzerota ' 
Peak of Teneriife from ship’s deck, 
Peak of the Azores, 
Temaheud, - - 
Mount Athos, 
Adam’s Peak, - - - 
Ghaut at the back of Tellichery, 
Golden Mount from ship’s deck, 
Pulo Pera from the Top of Penang, 
The Ghaut at Cape Comorin, 
Pulo Penang from ship’s deck. 
The last six observations, and that of the Peak of Teneriffe, 
were made by a writer in the Calcutta Monthly Journal. An 
example of a brig being seen in Scotland, at the distance of 95 
or 100 miles, by Captain Colby, will be found in this Journal, 
vol. i. p. 411. 
3. Hauyne. — From some good crystals of this rare mineral, 
which Dr Brewster has lately received from J. G. Cogswell, 
Esq. he has ascertained that it has no double refraction, and 
Authorities. 
Distance in 
Miles. 
Sir W. Jones, 
244 
Bruce, 
240 
- 1 
180 
- 
160 
. 
135 
. 
115 
Don M. Cagigal 
126 
Morier, .. 
100 
Dr Clarke, 
100 
.. 
95 
. 
94 
. 
93 
- 
75 
. 
73 
• 
53 
* Humboldt’s Personal I^arrativcy vol. i. 
been often seen at 30, 38, and 40 leagues, 
f Id. p. 99. Note, 
98. The Peak of Teneriffe has 
