466 Meteorological Observations for April 1831. 



lightning on two days, and thunder on one, two aurorse boreales, and seven 

 gales of wind, or days on which they have prevailed, namely, two from the 

 North-east, one from the East, and four from the S.W. 



AURORJE BOREALES. From half-past eight P.M. in the evening of the 

 19th till one A.M., an aurora boreali? appeared in the strong moonlight. 

 The streamers or columns of light began to ascend soon after nine; and 

 at twenty minutes past, the under edge of the aurora was best defined, 

 when its vertex in the magnetic north was 13| degrees above the northern 

 horizon, and at that time a perfect detached arch of the effluvium gra- 

 dually rose and disappeared. At forty minutes past nine there was a grand 

 display of about ten long active streamers along the under arch of the 

 aurora, several of which ascended to an altitude of 60 degrees ; and at a 

 quarter before ten, when they were most active, many passed beyond the 

 zenith through the square and tail of Ursa Major, exhibiting at the same 

 time several prismatic colours. At ten o'clock the arch of the aurora ex- 

 tended 150 degrees, and one of the coloured streamers, which rose from 

 the western point of the horizon, with a considerable inclination to the 

 South, passed over the moon, so that her light had but little effect over its 

 red colour, except in her immediate vicinity. The aurora now began to 

 sink gradually, but the red columns continued to rise at short intervals. 

 At twelve o'clock a cirrocumulus cloud sprang up from the North-east, in 

 a uniform arrangement of white flocks, and spread over the whole visible 

 hemisphere. After it had passed off, the streamers were again very active, 

 particularly in the North-east quarter, till one o'clock. One meteor ap- 

 peared over the aurora at ten o'clock, and the air was dry, with a clear sky 

 nearly the whole of the time. 



From a quarter past ten till twelve P.M. in the night of the 20th, parts of 

 an'arch of light were frequently formed instantaneously by a turbid coloured 

 fluid. The whole arch, extending from North-west by West to North- 

 east by North, was formed at intervals, but not more than 20 degrees or 

 25 degrees at a time, and it soon disappeared : its edge often coincided 

 with /3 Cassiopeia, then under Polaris, making its altitude about 20 degrees. 

 These sudden fits of light, about two degrees in width, were not produced 

 by any perceptible streamers of an aurora, but they must have emanated 

 from one under the horizon, and the coruscations in that case acted hori- 

 zontally in strong moon-light. Two bright meteors appeared over it. 



REMARKS. 



London. April 1. Fine: rain at night. 2. Cloudy: rain. 3. Fine. 

 4. Overcast : slight fog with frost at night. 5 7. Fine. 8. Heavy rain. 

 9. Cloudy: rain. 10, 1 1. Fine. 12. Cloudy : thunder with rain at night. 

 13, 14. Fine. 15, 16. Overcast. 17. Hazy. 18. Fine. 19. Fine : splendid 

 aurora borealis in the evening. 20. Fine. 21. Slight haze : fine. 22. Fine. 

 23. Cloudy : thunder at noon. 24 26. Fine. 27. Slight rain : fine. 

 28. Mild showers. 29. Rain, with intervals of warm sun. 30. Fine in the 

 morning : cloudy. 



Penzance. April 1. Clear. 2. Rain. 3, 4. Fair. 5. Clear. 6. Fair. 

 7. Fair: rain. 8. Fair: showers. 9 11. Fair. 12. Fair: showers. 

 13 21. Fair. 22. Fair: showers. 23, 24. Fair. 25. Rain: fair. 

 26. Fair. 27. Fair : rain. 28. Fair. 29. Rain. 30. Fair. 



Boston. April 1. Fine. 2. Cloudy: rain early A.M. 3. Cloudy. 

 47. Fine. 8. Rain. 911. Fine. 1217. Cloudy. 18. Fine. 

 19 25. Cloudy. 26. Fine. 27. Cloudy. 28. Rain. 29, 30. Cloudy. 



Meteoro- 



