prevalent Disorders, $c 9 with Volcanic Emanations, 437 



upper from the west, with rain, the dew point being 37°. On 

 the supposition of a cold current from above, many pheno- 

 mena of Nov. 12., and on the night of Nov. 13., may be ac- 

 counted for. (p. 161.) On the 12th there was a gust in the 

 Hudson, which upset a vessel, destroying all hands. On the 

 13th, a.m., there were similar gusts at New Haven, with an 

 increase of meteors. [See M. N. H., vii. 655. 9 on the fresh- 

 ening of the wind, Nov. 13. 1834.] Captain Parker, in the 

 Gulf of Mexico, as well as the vessel before mentioned, on 

 the Delaware, eighty miles from Philadelphia (p. 432.), had 

 the wind blowing directly from the cloud from which the 

 meteors emanated. 



Mr. Espy supposes that a very cold current of air from 

 the n.w., overlapping a warmer current from a southern point, 

 or an upper current from the north, moving faster than the 

 lower southerly current, would produce many vortices of 

 small extent, and, by intermixture of air, a cloud. Now, at 

 Philadelphia, no cloud was seen, though it was seen 80 miles 

 off; and, on the 12th, the air at the surface at Philadelphia 

 was 17° warmer than on the 11th, and 21° warmer than on 

 the 13th. If this position be allowed due weight, Mr. Espy 

 considers that it will account for the fall of the dew point; 

 the sudden blasts at the time caused by the downward vortices ; 

 the formation of the cloud ; the change of temperature ; and, 

 if the fifth query be answered affirmatively, the electrical 

 nature of the aurora. He considers the luminous clouds of 

 the night in question, on this supposition, to have formed an 

 interrupted conductor. He agrees, however, that it is not 

 determined, whether there was an upper current on the night 

 of Nov. 12. [1833] from the north-west, overlapping a "warmer 

 below (by which he means, containing more caloric to the 

 pound), and asks whether there has never been an upper cur- 

 rent of cold air overlapping an under one of warm air, since 

 the Bonpland meteors of 1799 ? [I refer the enquirer, for an 

 answer, to what I observed here on Nov. 12 — 13. 1834 [VII. 

 655."], and to Mr. White's observations on the same night 

 near London. [VIII. 97. 343].] Mr. Espy considers that, 

 judging from a variety of instances, these things must be sup- 

 posed to be connected together as cause and effect. 



On March 8. 1834, at 5\ p.m. the dew point was 59j° F. ; 

 and at 6 p.m., a shower having intervened, it had sunk 14°, 

 and was then clear. Next morning, at sunrise, the dew-point 

 was 15° above zero, having sunk 44|° in 13 \ hours. No 

 aurora was seen ; but, instead, " the tail of Mr. Olmsted's 

 comet had been seen on that night with uncommon brilliancy." 

 Again, from p.m. of March 29. 1834, to a.m. 30th, the dew 



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