Pn Ne a ee ee ee ee 
TRANSACTIONS OF THE SECTIONS. 15 
likely to’ conduct to the solution of this problem—a problem which must be solved 
before we can ascend with certainty to the physical causes of the phenomena. 
On the Results of the Magnetic and Meteorological Observations at General 
Sir Thomas M. Brisbane’s Observatory, at Makerstoun, in the year 1842. 
By J. A. Broun. 
The following are the points of chief importance in the paper. From acomparison 
of five months, ifi 1841, with the corresponding five months of 1842, the yearly 
movement of the north end of the declination magnet is about five minutes towards 
the east. The horizontal component of the earth’s magnetic intensity increases, and 
the vertical component. diminishes considerably in the year; the diminution of 
magnetic dip being about five minutes. A new method has been adopted in order 
to obtain the temperature corrections for the bifilar and balance magnets; it is 
described in the sixteenth volume of the Transactions of the Royal Society of Edin- 
burgh. It was mentioned that very consistent results had been obtained by dif- 
ferent methods of comparison of the uswal observations for the positions and tem- 
peratures of the magnets. When the observations of the balance magnetometer are 
corrected by this method, the diurnal range of the vertical intensity has been found, 
like that for the horizontal intensity and declination, to increase regularly from the 
winter months to the summer months. The annual period of the horizontal inten- 
sity, as deduced from thecorrected observations of the bifilar magnetometer for 1842, is 
striking ; a minimum of intensity occurs before or about each equinox, and a maxi- 
mum before or about each solstice. The observations at Toronto in Canada, in 1842, 
when corrected by the same method, indicate exactly the same periods, The monthly 
means for Makerstoun and Toronto were projected in curves, which were exhibited ; 
the two curves were almost identical, the increase of horizontal intensity being 
greatest in the end of the year at Makerstoun. ‘The gorrected observations of the 
balance magnetometer confirm in some sense the results from the bifilar, inasmuch 
as they also show the same annual periods of maxima and minima for the vertical 
intensity. As a severe test of the accuracy of the instruments and the methods 
adopted, the results for the magnetic dip deduced from the two force magnetometers 
were compared, both as to diurnal and yearly change of dip, with the results obtained 
from the inclinemeter, and they were found to agree very nearly. From the meteoro- 
logical observations, it was found that the range of the monthly means of the pres- 
sure of dry air was nearly the same as for the moist air. The mean of the three- 
monthly maxima and minima of temperature for each quarter of the year, was found 
to differ only by a fractional part of a degree from the mean of all the daily maxima 
and minima for the same period. The mean of the monthly maxima and minima of 
atmospheric pressure is less than the mean pressure for the whole year. This, it is 
conceived, has been found to hold always true, at least for places within the latitudes 
50° and 60° north; the reverse probably takes place in lower latitudes—it does so 
at Pekin; in 1841, the means of the monthly maxima and minima being in almost 
every month above the mean pressure. The curve of the relative humidity of the 
atmosphere for the year, deduced from the observations of the psychrometer, was 
shown to agree completely in its inflexions with the curve of the mean quantity of 
clouds covering the sky, this quantity being merely estimated. ‘ 
On a large Magnetic Machine. 
By the Rey. Witu1aM Scorzssy, D.D.,F.R.S.L. § E., Cor. Mem. Inst. France. 
The principal part of the machine consists of two cases, or fasciculi of magnetic 
bars, of unusually large dimensions, on principles developed in the author’s recent 
work, entitled ‘ Magnetical Investigations,’ which principles may be thus summarily 
stated :—1. That magnetic bars designed for large combinations may be conveniently 
constructed of various pieces. 2. That the separation of a long bar, say of three or 
four feet, into several portions, is not disadvantageous in regard to power ; and that the 
resulting power is similar, whether, in the combining of several series of short bars, 
the elementary bars be of the same or of unequal lengths. 3. That the relative 
‘powers of magnets, whether single or compound, when different in mass, but pro- 
