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proper plan of combined magnetic and meteorological observations. 

 Should the proposition to make this co-operation truly national, be 

 acceded to, the details in relation to it can easily be arranged, and the 

 Society will, the undersigned confidently believe, feel proud to lend 

 any aid in their power, in planning or executing them. It may per- 

 haps be more satisfactory however, to state briefly, beforehand, the 

 nature of the observations to be made, and the means required for 

 their execution. 



The magnetic observations to be undertaken at the fixed observato- 

 ries are, first, of the variation (declination), absolute horizontal inten- 

 sity and dip; second, of the changes of the variation of the horizontal 

 intensity, and of the vertical intensity. The regular observations for 

 changes in these elements, are to be made every two hours every day, 

 (with the exception of Sundays,) for the next three years, beginning 

 as soon as the several observatories can be arranged. To these are 

 to be added more frequent observations on one day of each month, 

 including the four terms during the year, fixed by the German Mag- 

 netic Association. At each station, a building of stone or wood will 

 be required, in the construction of which no iron must be employed. 

 The instruments adopted by the British observers are the following : 

 A magnetometer for the declination, one for the horizontal force, one 

 for the vertical force, a dipping needle, azimuthal transit, two reading 

 telescopes, and two chronometers. The estimated cost of each set of 

 these, is about fourteen hundred dollars. The cost of the observatory 

 must vary with the place at which it is erected, and the material 

 chosen for it, but may be estimated at from one thousand to fifteen 

 hundred dollars. One principal and three assistants will suffice for 

 making and reducing the observations at each station, and for carry- 

 ing on a supplementary series of meteorological observations. The 

 meteorological observations proposed, are on the pressure, tempera- 

 ture, and moisture of the air; on the direction and force of the wind; 

 on the quantity of rain ; on the temperature of the ground at different 

 depths; on solar and terrestrial radiation; besides a few miscellaneous 

 and occasional observations, not necessary to be here stated. Regu- 

 lar observations are to be made on these points, four times every clay, 

 and every hour on one day in each month. The instruments re- 

 quired at each station, are a barometer, a standard thermometer, a 

 maximum and minimum thermometer, a hygrometer, an anemome- 

 ter, several extra thermometers, an actinometer, and an apparatus for 

 atmospheric electricity. The probable cost of each set of these would 



