Proceedings of the British Association. 229 



period, we find a line of minima. We can, therefore, as previously 

 remarked, trace each of these distinct sets of barometric phenomena 

 in their own peculiar directions. It is, however, the reduction of the 

 observations to the level of the sea that enables us to do this : 

 the rise and fall at any one station, as exhibited by curves (times 

 being used as abscissae) give the combined effects of the three 

 systems ; and unless they are separated by taking the distances of the 

 stations into account, we are perplexed with the apparent irregularity 

 of the atmospheric changes. 



Sir J. Herschel said it was a remarkable circumstance, that Mr. 

 Birt had been able to trace so close a connection between phenomena 

 which had been observed at such distant places, and with consider- 

 able intervals of time. The subject promised to lead to important 

 results. 



' On the Results of the Magnetic and Meteorological Observations 

 at Sir Thomas Brisbane's Observatory, at Makerstown, in the year 

 1842/ by J. A. Broun. — The following are the points of chief im- 

 portance in the paper. From a comparison of five months, in 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 intensi- 

 ty 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 magnet; it is described in 

 the sixteenth volume of the Transactions of the Royal Society of 

 Edinburgh. It was merely mentioned that very consistent results 

 had been obtained by different methods of comparison of the usual 

 observations for the positions and temperatures 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 intensity as deduced from the correct- 

 ed observations of the bifilar magnetometer for 1842, is striking; 

 a minimum of intensity occurs before or about each equinox, and 

 a maximum before or about each solstice. The observations at 



