TllANSACTIONS OF SECTION A. 



f)30 



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

 scieutitlc purposes. 



(]. Report nf the Committee for cDiisulerinri the lest methods of rcconJhij 

 the direct intensihj of Solar liadiulion, — See Boports, p. '28. 



Fourth lieport of the Cuminittee on Meteoric Dust. — Seo Reports, p. 38. 



to 



8. 0)1 the Siiot Spectrum from B to B. Bij the Rev. S. J. Peuuy, F.E.S. 



The observations of tlio red end (.f tlio spot spectra, made at Stonyhurst 

 01)SL'rvat(iry in lS8.'i, aliimled ^'ood prmif of the existence in solar spots of I'e, Ca, 

 Xa, II, Ti, J)!i, and Xi, and aLo fair indicut ions df nniny other suljstances. They 

 likewise showed that the line of AV.L. G(''77'0 belongs to the spectra of both spots 

 and clironiospliere. 



Durin<^ the course of the current year the wideniiifr of 240 I'nes between Ti and 

 J) lias been detected, o", of which belon;^ 1o 1<V, li* to Ti, 4 i Xi, 4 to Xa, and 

 others to Ca, 15a, Mn, !kc. 



Faint lines are most alTeeted by tlio selective absorption of spot vapours, Ti, 

 Fe, and Xa, ollerinpr numerous examidi's. 



Jjines not visible in the solar sjieelruni are often seen in spot spectra, and the 

 pi'inimbra aifects lines in some cases almost us nuieli as tlie umbra. 



Dill'eri'nt elements are Avidened in ditlerent spots, and the lines of the same 

 element are diflierently atl'eeted. 



The wideni]i<r of the 1) lines on the violet side only aflbrds evidence of a. 

 decided nprush in certain spots. 



Lastly, attention sliould bo drawn to the fact that lines, marked as telluric 



o 



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

 of the photosphere in the immediate neighbourhood. 



9. On Becent Frogress in Photographing the Solar Spcctncvi. 

 By Professor H. A. Rowland. 



10. On an Induction Inclinometer adapted fur Photographic Begistration. 

 By Charles Carpmael, M.A. 



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

 ziioditications consisting in — 



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



2. The placing of the induction bars at sucli 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 posnion. 



Stops are employed to ^>r('vent the magnet from turinng much beyond the limits 

 of the scale; as, if either ])ole 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 permanrnf magwatism of the induction bars is 

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

 force, which will, however, afliict the scale coefhcient. Except in great disturl)- 

 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 



II 



