230 Proceedings of the British Association. 



Toronto in Canada, in 1842, when corrected by the same method, 

 indicate exactly the same periods. The monthly means for Maker- 

 stown and Toronto were projected in curves, which were exhibited ; 

 the two curves were almost identical, the increase of horizontal in- 

 tensity being greatest in the end of the year at Makerstown. The 

 corrected observations of the balance magnetometers 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 true force 

 magnetometers were compared, both as to diurnal and yearly change 

 of dip, with the results obtained from the inclinometer, and they were 

 found to agree. From the meteorological observations it was found 

 that the range of the monthly means of the pressure 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. 



The Astronomer Royal said that he was not quite certain that he 

 understood Mr. Broun' s proposed method of eliminating the effect 

 of temperature on the magnetic force ; but if he did, then he must 

 protest against it, since the power of the needle itself, as well as 

 the magnetic force of the earth, were affected by the changes of tem- 

 perature, the effects of which he had eliminated. — The Rev. Dr. 

 Lloyd said, it was found that it was absolutely necessary to subject 

 the magnet artificially to considerable differences of temperature, in 



