TRANSACTIONS OF THE SECTIONS. ll 
the Astronomer Royal, a distinguishing electrometer, formed on the dry pile system, 
was afterwards employed, which exhibited in the photograph, not only the tension, 
but the kind of electricity possessed by the electrometer at any given time. The dry 
thermometer was next tried. It was of the horizontal kind, had a flat bore, and its 
tube was introduced through the side of the microscope. The tube had a diaphragm 
of very narrow aperture fixed upon it, and the slit in the screen, at the eye-end of the 
microscope, was now of course straight and horizontal. The image was a little mag- 
nified, and the breadth of the dark band or line in the photograph became the mea- 
sure of temperature inversely at any given time*. ~The barometer employed was of 
the siphon kind. The microscope was turned in order to bring the long case and its 
sliding frame into a horizontal position. The clock was placed at one end, and a 
little weight, sufficient to keep the frame steady, was suspended by a line passing over 
a pulley at the other. The lower leg of the barometer was introduced through the 
now bottom of the microscope; it was provided with a similar kind of diaphragm to 
that on the thermometer, and of course the slit in the screen was now vertical. A 
light blackened pith-ball rested on the surface of the mercury, and its image was 
slightly magnified, but will in future be much more so. The declination magnet was 
one of two feet, lent to Mr. Ronalds by the Astronomer Royal. It was provided with 
a damper, and its mode of suspension was essentially similar to that of the Greenwich 
declinometer. In order to adapt it for self-registration, a light conical brass tube, 
projecting six inches beyond its north end, was affixed to the lower side of the spur 
which carried it, and to the north end of that tube a small wire, called the index, was 
attached at right angles. This index descended through little slits in the bottoms of 
the two cases which enclosed the magnetic, and took the place of the electrometer 
in the lucernal microscope, which was placed below the cases, and was now required 
to be much longer than before, in order that the image and motion might be suffi- 
ciently magnified, yet a flat field retained. Everything was firmly fixed upon the two 
pillars which formerly carried the transit instrument of His Majesty George III, A 
great many photographs were obtained and sent for inspection to Greenwich. Con- 
cerning some term-day impressions, Mr. Glaisher, the Magnetical and Meteorological 
Superintendent of the Greenwich Observatory, says, in an official note, that “the 
beautiful agreement of the results with these at Greenwich is highly satisfactory.” 
On some Meteorological Phenomena. By Professor WARTMANN. 
Although many attempts have been made of late to extend our knowledge of ‘the 
electrical phenomena of the atmosphere, it must be confessed that much remains to 
be done. The frequency of the flashes of lightning, according to the latitude to the 
seasons, is a subject of inquiry which has been recommended.by M. Arago. It 
would also be interesting to record the duration of thunder-storms, the number of 
flashes of each of the three classes which have appeared, the height and general 
appearance of the clouds, and the hygrometric state of the atmosphere. ’ 
I shall take the liberty to point out some facts which I had occasion to witness on 
the evening of the lst of August last. After many hot days, clouds appeared on 
the south-west part of the horizon of Lausanne, and when over the town they began 
to become illuminated almost without interruption. I counted more than forty flashes 
in twenty-two minutes, two-fifths of which were of the first class, and all going 
eastward. 
A flash, of such a white byilliancy that the eye could not bear it, but the appear- 
ance of which was perfectly definite, did not disappear suddenly, but left a florescent 
trace of a dark red colour, like to the illusions of the dissolving views and the trainées 
or trails of certain shooting stars which I observed on the night of the 10th of 
August 1838. 
Another flash of the first class appeared at the under part of the clouds, and after 
a rather long course, it vanished at the very edge of it: no thunder was heard. 
Two flashes were bicuspidated ; three others were tricuspidated at some distance from 
their origin, two of which appeared together, one over the other, in the same hori- 
* Tn order to convert this into the wet bulb hygrometer, nothing of course is necessary but 
the application of the usual cup of water and the capillary threads. 
