473 Scientific Intelligence. [Dec. 



found a much greater proportion of muriate of magnesia than 

 Marcet, It is difficult to say on which side the error lies. In 

 consequence of the great care which Dr. Marcet took, and the 

 number of times that his analysis was repeated, I rather feel 

 disposed at present to prefer his results ; but another analysis 

 by some other person, with all the precision that our present 

 analytical methods admit, will be necessary before the point can 

 be considered as settled. 



Gay-Lussac found traces of muriate of potash in this water. 

 He exposed it to a temperature of 19° without any crystallization 

 taking place. Hence it follows that the water of the Dead Sea 

 is not saturated with salt. 



VII. Beautiful luminous Phenomenon. 

 (To Dr. Thomson.) 

 SIR, Newton Stewart, Oct. 18, 1819. 



A singular and beautiful phenomenon appeared in our atmo- 

 sphere here last night about eight o'clock ; it was a bow, or 

 arch, of silvery light, stretching from east to west, and intersect- 

 ing the hemisphere at a few degrees to the southward of the 

 zenith ; its breadth varied considerably during its continuance ; 

 but when in its most perfect and defined state might have formed 

 with the eye an angle equal to what the breadth of the rainbow 

 generally does. The intensity of its light might be compared to 

 that of a thin cloud illumined at night by the moon, and was 

 greatest towards the extremities of the arch, both of which were 

 lost in dark clouds. I was not an eye-witness to its formation, 

 but was told it first shot up from the eastern horizon^ After it 

 had remained very bright for 20 minutes, or so, dark blanks 

 were first observed to take place here and there ; then after 

 expanding a little in breadth, and shifting for a short way further 

 to the southward, it disappeared. Some time before its appear- 

 ance, the atmosphere had been very cloudy; but when it was 

 formed, the sky was free of clouds, except towards the horizon, 

 to the westward and northward, where they hung very dark and 

 heavy. It was also a calm, but the wind had been at N. the 

 barometer stood high, and the thermometer at 43°. To account 

 for such a singular phenomenon, I make no pretensions ; but it 

 was strikingly different from any of the usual forms of the boreal 

 lights, which too were seen very vivid in the course of the even- 

 ing. From its steady permanence for such a long time, the body 

 illumined could be recognised as of a vapory nature, and the 

 stars were discernible through its medium at several places. 



The above appearance was observed with a great degree of 

 interest and admiration by all who saw it; and I have transmitted 

 you this notice of it, judging that it will not be unacceptable to 

 you, or uninteresting to some of the readers of your Annals of 

 Philosophy. I am, Sir, with, respect, B.. . 



