Mr. Maclear on a Luminous Arch seen on March 23. 373 



I could sav more, but I fear I have already taken up too 

 much of your space with tl.ls subject. Yours truly, 



Philadelphia, Deo. 17, 18x^8. Jacob Grlen. 



LV. On a Luminous Arch seen at Bigglesivade on the 23rd 

 of March. By Mr. Thomas Maclear. 



To Mr. Taylor. 

 Sir, 



ON Monday morning last (the 23rd instant), at 14" 20" 

 sidereal time, 1 observed a luminous arch of white light 

 extending itself from the eastern horizon, from the point E. 

 by S. towards a Ursae Majoris, and to within eight degrees of 

 the meridian. It was four degrees broad at the horizon, gra- 

 dually increasing to six at the altitude of forty. Its north 

 edge accurately defined. 



At 14^ 24"" a Lyras was seen distinctly shining through its 

 middle. It bifurcated at the altitude of 11°, diverging to 8° 

 in breadth at the meridian, reaching 8 Ursas Majoris ; the 

 northern limb in the direction of Polaris. 



The wind E. by N., very low. 



A slight appearance of aurora borealis in the North, but 

 rendered dim by the moonlight. 



At l^'' 26™ divided into three branches: aLyrae in the most 

 southern. 



At l*** 30™ divided into four branches. 



At 14-'' 32"* divided into five branches. The spaces be- 

 tween the three northern very clear and well defined, a Lyrae 

 on the south edge of the most southern. 



At \^^ 35™ ibrmed two beautiful arches, Polaris between 

 them : a Lyrae 6° clear of the most southern. 



A few streamers shooting from the West towards Polaris 

 to about the altitude of 10°. 



At 14''' 39™ the southern arch fading; white flocculent 

 clouds obscuring the moon. 



a few remarks from us. Mr. Campbell's anticipation of Dr. Green's expe- 

 riment with a t;lass vessel hermetically scaled, has been noticed in pre- 

 ceding [laL'e; and Dr. G.'s observations on the cooling of the pitch by the 

 dinunislied teni[)crature of the deep water, tend, as it appears to us, to 

 confirm Mr. Sowerby's opinion. Tlie api)earancc and dnctility of pitch at 

 temperatures of moderate warmth only, are alinded-to by Mr. Sowerby, 

 whose remark has no reference to its jitpiefaction ; and the fact that the 

 ocean at a consideral)lc depth is much colder than at the surface, is the very 

 pround of that {gentleman's statement on this jiart of the subject. Some 

 experiments with wine-l)ottles secured with pitch, &c. made by Mr. Camp- 

 bell at the same time he sunk the -;lobnlar bottles already mentioned, also 

 appear to confirm Mr. Sowcrl)y's observations.— Euir. 



At 



