394 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1730. 



altitude varied a little, but never reached higher than the head of Orion, 

 which was 54° high, and never was seen lower than a little under Procyon, 

 which is an altitude of 45 or 46°. The inferior arch was exactly parallel to the 

 superior, and the breadth of the zone varied from 14 or 15° to 18 or 20°. 



The colour of this zone was red, scarlet, inclined to purple, pretty lively 

 and changeable by intervals. It was less vivid near the horizon, and also to 

 the meridian, where it seemed now and then interrupted. Some imagined two 

 great arches rising, one from the east, the other from the south-east, and 

 meeting together near the meridian, but immediately afterwards parting, and 

 drawing back, which they repeated very often. 



Under this zone was to be seen, but not constantly, one or two lucid and 

 interrupted arches, which comprehended with the horizon a dark segment very 

 like a mist. 



It was remarkable, that this Aurora considerably darkened the light of those 

 stars which were seen through it; and that was much more true of the red 

 meridional zone, which died with its reddish colour the stars that appeared 

 behind. When that zone was the highest, it covered Jupiter; and some gen- 

 tlemen, which at that time had not yet remarked the Aurora, looking at Ju- 

 piter through a telescope, affirm they could hardly see it, but that it seemed 

 as intercepted by some dark cloud; and indeed it looked at that time as if it 

 had been seen through a red glass. 



This observation confirms what is moreover very probable, that this zone 

 was produced by the light of the opposite Aurora, either by reflection or re- 

 fraction. But the manner of its production seems difficult to be accounted 

 for. There may be supposed icy particles swimming in the air, and of such 

 figure as to exhibit a great zone, by the reflection and refraction of the light of 

 the Aurora, almost in the same manner as the drops of rain produce the ap- 

 pearance of the rainbow. But this is mere conjecture. 



Of a Spiritus Fini yEthereus ; luith several Experiments tried with it.* By Dr. 

 Frobenius, F.R.S. N° 413, p. 283. 



Exper. 1. — The ether of plants appears to be almost destitute of all gross 

 air, from placing it under the receiver of the air-pump; for exhaust the air 



* Bergman (Phys. and Chein. Essays, Vol. III. p. 109, English Transl.) relates, that the methotl 

 of preparing ether was first described, under the name of Ol. Vitr. dulce, by Valer. Cordus in 1542, 

 and that there are some obscure traces of it in Basil Valentine; but the above appears to be the first 

 distinct account of some of its most remarkable properties. It is uncertain whether Frobenius was 

 a real or a fictitious name, but he was a native of Germany. A particular account of his process 

 for preparing the ethereal liquor was not published until several years alter, in the 4l8t vol. of the 

 Philos. Trans. 



