216 
THE ASTRONOMER ROYAL 
in the same way, in curves, drawn with great care by Mr. William Carpenter Nash, 
Assistant in the Magnetical and Meteorological Department of the Royal Observatory. 
While submitting these curves to the examination of the Royal Society, as presenting to 
the Society the evidence on which conclusions as to the relation between the galvanic 
currents and the magnetic disturbances must rest, I remark that the class and complete- 
ness of the evidence which they afford appear to be precisely similar to those offered by 
the curves appended to the First Memoir, and that the necessity for multiplying copies 
of them is not, perhaps, very pressing. 
The conclusions arrived at in the former investigation were these : — 
1. The general agreement of the curves, especially in the bold inequalities, is very 
striking; particularly in the curves relating to Northerly Force. 
2. The small irregularities in the curves of galvanic origin are more numerous than 
those in the curves of magnetic origin. 
3. The irregularities in the curves of galvanic origin usually precede, in time, those 
of magnetic origin, especially as regards Westerly Force. 
4. 'l'he proportions of the magnitudes of rise and fall in the curves often differ sensibly, 
especially as regards Westerly Force. 
5. The Northerly Force appears, on these days of magnetic storms, to be increased; 
whereas general experience leads us to expect that it would be diminished. 
These conclusions are all supported by examination of the curves formed from the new 
investigations ; I am still unable to suggest any explanation of the 2nd, 3rd, and 4th, 
and I still offer them as subjects worthy of the most careful inquiry. In considering the 
possibility of explaining any of them by instrumental causes, it appeared to me that the 
only one, for the effects of w Inch there could be any opening, is, fault in the Declination- 
Magnetometer. By the courtesy of the Committee of the Kew Observatory, I was per- 
mitted to compare the Greenwich Declination-Photograms with the Kew Declination- 
Photograms, and I found them absolutely identical. I therefore abandon the expectation 
of explaining the conclusions as the effect of instrumental error. 
On the 5th conclusion, much light will be thrown by the examination of the pheno- 
mena of days of tranquil magnetism. 
I now proceed with the discussion of the curves exhibited by the Earth-current Pho- 
tograms on days of tranquil magnetism. No comparison was made here between the 
results of the Earth-current Curves and the Magnetometer Curves; my object being 
merely to examine the laws, as regards diurnal inequality, of the Terrestrial Galvanic 
Currents, or rather of the Northerly and Westerly Magnetic Forces which those currents 
might be expected to produce. 
It was necessary that the process to be employed should be precisely equivalent to 
that used on the days of magnetic disturbance ; but there was advantage in changing 
the form. For, where every individual disturbance was to be depicted, it was necessary 
to measure every individual ordinate by two different scales ; here, where the mean of 
