TRANSACTIONS OF SECTION A. 635 



shall be taken, to be subsequently reduced and made available for practical and 

 scientific purposes. 



6. Report of the Committee for considering the lest methods of recording 

 the direct intensity of Solar Radiation. — See Reports, p. 28. 



7. Fourth Report of the Committee on Meteoric Dust. — See Reports, p. 38. 



8. On the Spot Spectrum from D to B. By the Rev. S. J. Perry, F.R.S. 



The observations of the red end of the spot spectra, made at Stonyhurst 

 Observatory in 1883, afforded good proof of the existence in solar spots of Fe, Ca, 

 Na, H, Ti, Ba, and Ni, and also fair indications of rnany other substances. They 

 likewise showed that the line of "W.L. 6677 - 6 belongs to the spectra of both spots 

 and chromosphere. 



During the course of the current year the widening of 240 lines between B and 

 D has been detected, 55 of which belong to Fe, 12 to Ti, 4 to Ni, 4 to Na, and 

 others to Oa, Ba, Mn, &c. 



Faint lines are most affected by the selective absorption of spot vapours, Ti, 

 Fe, and Na, offering numerous examples. 



Lines not visible in the solar spectrum are often seen in spot spectra, and the 

 penumbra affects lines in some cases almost as much as the umbra. 



Different elements are 'widened in different spots, and the lines of the same 

 element are differently affected. 



The widening of the D hues on the violet side only affords evidence of a 

 decided uprush in certain spots. 



Lastly, attention should be drawn to the fact that lines, marked as telluric 



O 



in Angstrom's map, are not unfrequently wider in spot spectra than on the surface 

 i if the photosphere in the immediate neighbourhood. 



On Recent Progress in Photographing the Solar Spectrum. 

 By Professor H. A. Rowland. 



10. On an Induction Inclinometer adapted for Photographic Registration. 

 By Charles Carpmael, M.A. 



The instrument is a modification of Lloyd's Induction Inclinometer, the 

 modifications consisting in — 



1. The substitution of a bifilar for a unifilar suspension. 



2. The placing of the induction bars at such a distance apart that, when the 

 dip has approximately its mean value at the place, the suspended magnet may be 

 in equilibrium at right angles to the magnetic meridian, under the action of the 

 magnetic forces alone, the torsional force of the suspension threads having been 

 made to vanish in that position. 



Stops are employed to prevent the magnet from turning much beyond the limits 

 of the scale ; as, if either pole of the magnet is allowed to approach too near to 

 the soft iron bars, their magnetic condition is permanently changed. 



With this arrangement, if the permanent magnetism of the induction bars is 

 eliminated, the reading in the mean position is unaffected by changes in the total 

 force, which will, however, affect the scale coefficient. Except in great disturb- 

 ances, therefore, no correction for force need be applied. Small changes in 

 declination will not affect the readings, so that the instrument is well adapted for 

 photographic registration of changes of the dip. 



The permanent magnetism may be eliminated from each bar separately, _ by 

 setting it in vibration when in the position in which the permanent magnetism 



