Meteorological Observations for April 1829. i67 



ton 1)V the upper part of a semi-halo whose diameter was 59 degrees, and 

 at the intersection the colours were extremely bright. The arcs of mter- 

 sected halos are very generally reversed to each other, but these formed an 

 exception the exterior semi-halo having the same position as the upper part 

 of the perfect halo, only its diameter was 14 degrees wider, which perhaps 

 was occasioned by two strata of hazy clouds that appeared at different al- 

 titudes at the time; for had the enlarged semi-halo been caused by reflec- 

 tion the arcs of both would have been parallel, the same as the ins and 

 its reflected bow. At 10 P.M. on the 8th, a faint lunar ins appeared to 

 the eastward in a passing nimbus. This is a rare meteoric phaenomencn, 

 and is eenerally seen at the expense of a wetting. , , , . , 



The effect of the strong gales from the S.E. and S.W. on the 14th, sunk 

 the barometer unusually 'low; nor have we had so low a monthly mean 

 pressure of the atmosphere since February 1823. On the 1/th two swal- 

 lows were observed here, being the first time of their appearance this 



^'^The mornin" of the 24th was warm, and by noon the exterior thermo- 

 meter in the sliade had risen to 65 degrees, when glows of heat \vere felt 

 from surrounding cumulostratus ; but the maximum temperature of the ex- 

 ternal air on the following day was 24 degrees lower 1 and it being three 

 or four deo-rees less than that which elicits dew from the atmosphere, a de- 

 position of dew on the inside of the glass windows continued from 10 A.M. 

 till 4 P M., when the rain, sleet and large flakes of snow ceased. Ihe 

 temperature of the external air during that time varied from 41 degrees to 

 .39 decrees, and of that in a room with a small fire from 50 degrees to 48 

 de^rels; the corresponding averages being 40 degrees and 49 degrees the 

 metn of which, after the inosculation of the external with the internal air, 

 is 44J decrees for the dew or vapour point, which nearly agrees with more 

 delicate experiments in ascertaining the degree of temperature requisite 

 for the production of dew. The mean temperature of the air tins day vvas 

 12i de<n-ees colder than the mean of the same day of the month for the 

 last 14° years; and the mean temperature for the month is more than a 

 de<'ree under the mean of April for the same period. 



the wind blew in very heavy gusts from the N.W. on the 28th, and 

 from the N. on the 29th; and in London, Liverpool, Scotland, and Ire- 

 land, it was felt as a hurricane, where it did considerable damage. 



The atmospheric and meteoric phaenomena that have come within our 

 observations this month, arc one parhelion, five solar and two lunar halos 

 one lunar and three solar rainbows, two meteors, thunder once, and 

 twelve gales of wind, or days on which they have prevailed ; namely, one 

 from the North, two from the North-east, two from the East, one from 

 the South-east, three from the South, two from the South-west, and one 

 from the North-west. 



REMARKS. 



London.-h\m\ 1. Fine. 'J. Slight fall of snow in the morning : stoi-my. 

 '5 Stormy with slight snow-showers. 1. (Jhjiuly : rain at night. r< 7. 

 Showery h. 0. Wet. 10. Fine, with slight sliowers. 1 1. Imuc : heavy 

 rain at ni-ht. ' 1 2. Showery : stormy at night. 1 ;i. Fine mornnig : sho« cry. 

 11 Fine "rainy in the ailernoon, with a iioisterous gale duniig the iiigiit. 

 1 5 Stormy, wi'th showers, with a boisterous gale during the njght. IG. 

 licavy rain : fine at night. 17. Fine, with showers. 18, li). I-me in the 

 morning : showery. 2(). Cloudy, with showers. 21. Slight fi-g in nmining : 

 very fine. 22. Ilcavy rain. 2:!. Cloudy morning: line. 2 1. l^iomly. 

 ■_";. Stormy and wit. 2«. Very fine. 27. Rainy. 28. Stormy, with sliov.ers 

 anil strong gale. 29. Slorinv. ;io. Cloudy. 



